The detachment of a feed roller rotatably supported by a holding portion provided in the main body of an apparatus, and held detachably in the axial direction thereof is restricted by a locking device. The locking device is made movable to a lock position and a lock releasing position for permitting the detachment of the feed roller. Further, when the locking device is in the lock releasing position when a sheet stacking portion is mounted, the locking device is moved to the lock position by a position changeover device in operative association with the mounting operation of the sheet stacking portion.