A developing device includes a frame, a cylindrical developer carrying member, and a regulating member including a contact portion. When a position of the contact portion where a maximum of a pressure distribution of the contact portion to the developer carrying member with respect to a rotational direction of the developer carrying member is indicated is a reference position, the contact portion includes a first region positioned upstream of the reference position and a second region positional downstream of the reference position with respect to the rotational direction. The contact portion has surface roughness smaller in the first region than in the second region. The surface roughness in the second region is 20% or less of an average particle size of toner particles contained in the developer.

A method of attaching a regulating blade made of resin to an attachment portion of a development frame which is made of resin and includes the attachment portion for attaching the regulating blade includes applying an adhesive to the attachment portion, applying a hardening accelerator to the regulating blade, and attaching the regulating blade to the attachment portion via the adhesive applied to the attachment portion and the hardening accelerator applied to the regulating blade. The regulating blade is disposed opposite to and not in contact with a development rotary member configured to bear and convey a developer toward a position at which an electrostatic image formed on an image bearing member is developed, and configured to regulate an amount of the developer to be borne on the development rotary member.

A method of attaching a regulating blade made of resin to an attachment portion of a development frame which is made of resin and includes the attachment portion for attaching the regulating blade includes applying an adhesive to the attachment portion, applying a hardening accelerator to the regulating blade, and attaching the regulating blade to the attachment portion via the adhesive applied to the attachment portion and the hardening accelerator applied to the regulating blade. The regulating blade is disposed opposite to and not in contact with a development rotary member configured to bear and convey a developer toward a position at which an electrostatic image formed on an image bearing member is developed, and configured to regulate an amount of the developer to be borne on the development rotary member.

A restricting member includes a blade portion and a supporting portion. A contact portion is provided at the blade portion, and, in a cross section orthogonal to a longitudinal direction, the contact portion includes a first portion extending in a first direction and a second portion extending toward a free end from an end of the first portion and extending in a second direction. When a region demarcated by connecting an intersection point, the end of the first portion, and an end of the second portion by a straight line is defined as a first region, the intersection point being where an imaginary line intersects an extension line of the first portion in the first direction, an area of the first region is smaller on a longitudinal end portion than on a longitudinal central portion of the blade portion.

A developing device includes a supply member, a developing device body, and a closing member. The supply member supplies a developer to an image holding element that holds a developer image. The developing device body rotatably supports the supply member. The closing member closes a clearance formed between the developing device body and the supply member with one end of the closing member fixed to the developing device body and the other end, which is a free end, contacting the supply member. The closing member has plural grooves formed to extend from the other end toward the one end.

A developing apparatus includes a developer bearing member; and a regulating member configured to come in contact with the developer bearing member, and regulate the thickness of the layer of the developer. The contact surface of the regulating member with the developer bearing member satisfies 3Rz<20 (m), 30Sm100 (m), and Vmp0.05 ml/m.sup.2 where Rz represents a maximum height roughness, and Sm represents an average interval of unevenness, and Vmp represents a volume in an initial state of a protruding peak part in parameters in a three-dimensional surface roughness defined in ISO 25178.

A developing cartridge includes a housing for accommodating a toner, a developing roller rotatably mounted in the housing, a doctor blade in contact with the developing roller, and a driving device located at a longitudinal end of the housing. The driving device includes a driving force receiving part for receiving a driving force from the outside of the developing cartridge, and is configured to drive the developing roller to rotate. The doctor blade is in contact with a surface of the developing roller to adjust a thickness of a toner layer on the surface of the developing roller. When viewed along a longitudinal direction of the developing cartridge, at least the driving force receiving part does not overlap with the doctor blade.

A developing device includes a cylindrical developing roller, a regulation member, a magnetic member, and a synthetic resin member. The regulation member includes a first opposing surface facing an outer circumferential surface of the developing roller. The magnetic member is arranged on a side surface of the regulation member. The synthetic resin member is arranged on a side surface of the magnetic member. The synthetic member includes a second opposing surface facing the outer circumferential surface of the developing roller. The second opposing surface is tilted at 40 or more but 60 or less with respect to the first opposing surface to be increasingly distant from the outer circumferential surface of the developing roller toward an upstream side in a rotating direction of the developing roller. A solubility parameter of a material of the synthetic resin member is 23 (J/cm.sup.3).sup.1/2 or more. Magnetic toner contains toner and resin fine particles.

A developing device of developing a latent image formed on an image bearer includes a developing roller, a developer regulator of a round-bar shape, and a holder. The developing roller carries developer. The developer regulator faces the developing roller to regulate an amount of the developer carried on a surface of the developing roller. The holder has a first hole, a second hole, and a projection. An end of the developer regulator is inserted in the first hole. A shaft at an end of the developing roller is inserted in the second hole. The projection protrudes toward an inside of the at least one of the first hole or the second hole and holds the end of the developer regulator and the shaft.

A restricting member includes a blade portion and a supporting portion. A contact portion is provided at the blade portion, and, in a cross section orthogonal to a longitudinal direction, the contact portion includes a first portion extending in a first direction and a second portion extending toward a free end from an end of the first portion and extending in a second direction. When a region demarcated by connecting an intersection point, the end of the first portion, and an end of the second portion by a straight line is defined as a first region, the intersection point being where an imaginary line intersects an extension line of the first portion in the first direction, an area of the first region is smaller on a longitudinal end portion than on a longitudinal central portion of the blade portion.