An image forming apparatus includes a transfer portion; a fixing portion; a detection unit that is capable of detecting a deflection amount of the recording material; and a controller configured to control a conveying speed of the fixing portion. The detection unit has a contact portion and a detection portion, and the contact portion is movable to a first position and a second position. The controller moves the contact portion from the second position by outputting the signal for setting the conveying speed to a second speed larger than the conveying speed when the contact portion is located at the second position, and the controller determines an abnormal state when the contact portion is located at the second position and an output time of the signal is longer than or equal to a predetermined time.

An image forming apparatus includes an image forming portion, a fixing device detachably mounted on a main assembly of the image forming apparatus and a moving mechanism. The fixing device includes a detecting flag contacting a back surface of the recording material. The detecting flag is positioned in a first position within a conveyance path when the recording material does not exist on the detecting flag and moves in a direction toward the back surface from a front surface relative to the first position when the recording material exists on the detecting flag. The moving mechanism causes the detecting flag to move so as to position the detecting flag in the first position when the fixing device is mounted on the main assembly and in a retracted position when the fixing device is demounted from the main assembly.