An upper frame member is pivotally attached to an apparatus body so as to pivot between a closed position and an open position. The apparatus body is closed when the upper frame member is in the closed position, and the apparatus body is opened to expose an image forming unit when the upper frame member is in the open position. A locking member locks the upper frame member to the apparatus body when the upper frame member is in the closed position. An operation member positioned on a sheet stacking surface releases the locking member to unlock the upper frame member from the apparatus body.
