A method for processing a sheet at a predetermined position on the sheet in a processing part, includes: placing a plurality of the sheets in a placement part; reading, by a first reader disposed in the placement part, information printed in a predetermined area on the sheet spaced apart from a trailing edge of the sheet by at least a first length, the first length being the length in a plan view from a disposed position of a detector to a disposed position of a contact member with which leading edges of the sheets placed in the placement part come into contact, the detector detecting the sheet on a conveyance path for the sheet extending from the placement part to the processing part; and processing the sheet based on the information read by the first reader.

A sheet processing apparatus includes a first guide plate and a second guide plate facing with a given space in a thickness direction and having second and third openings, a sheet conveyance passage between the first and second guide plates, and a sheet conveyor including a drive source, a drive roller, a first driven roller, and a second driven roller. The drive roller protrudes from the first guide plate toward the sheet conveyance passage through the first opening. The first driven roller faces the drive roller and protrudes from the second guide plate toward the sheet conveyance passage through the second opening. The second driven roller protrudes from the second guide plate toward the sheet conveyance passage through the third opening. The second driven roller is disposed at a position shifted from the drive roller in a width direction orthogonal to the sheet conveyance direction and the thickness direction.

A sheet post-processing device includes a conveying member, a processing tray, a processing section, a reference plate, an alignment member, a holder drive unit, and a control unit. The alignment member includes a paddle holder, and an alignment paddle having a paddle main body supported in a rotatable manner at the paddle holder, and a paddle part protruding from the paddle main body. The holder drive unit moves the alignment paddle in a reciprocating manner, between a reference position to separate the paddle part above a top sheet and an acting position to allow the paddle part to contact with the top sheet. The control unit sets a second acting position when the paddle part contacts with the sheet at n1-th time, to be higher than a first acting position when the paddle part contacts with the sheet at m1-th time, where 1m1<n1 holds.

A sheet binding device includes a processing tray, a movable reference plate, a stapling portion, a movement portion, a slide member, and a slide spring. When the stapling portion in an inclined state is moved from a reference position to a stapling position, the movable reference plate moves from an initial position, and when orientation of the stapling portion is shifted from the inclined state to a parallel state, the movable reference plate returns to the initial position. When the orientation of the stapling portion is shifted from the parallel state to the inclined state while the stapling portion is moved from the stapling position to the reference position, the movable reference plate moves from the initial position, and the stapling-side engagement portion separates from the movable engagement member, thereby causing the movable reference plate to return to the initial position.

When discharging a sheet onto a discharge tray, a control unit sets position of the discharge tray in an up and down direction to a predetermined discharge position. When loading the sheet onto a processing tray, the control unit sets the position of the discharge tray in the up and down direction to a loading position lower than the discharge position.

A paper creasing device includes a receiving member including a groove extending in a fixed direction; a rotary blade movable along the groove; and a movement mechanism for moving the rotary blade along the groove at a fixed height in a range between first and second edges of paper in a width direction, the paper being placed on an upper surface of the receiving member. The receiving member is formed to have shearing forces applied to the paper sandwiched between the rotary blade and the groove in an outside range and an inside range in the width direction of the receiving member, the outside range corresponding to at least one of the paper edges located on a side where the rotary blade starts contacting the paper when moving along the groove, and the shearing force in the outside range being smaller than the shearing force in the inside range.