In a storage structure formed in the lower door of a back door connected to the rear opening of a vehicle, a cover body (30) for opening/closing an opening is attached to a storage member (20) fitted into a recess formed in the inner surface of the lower door. The cover body (30) can be changed between a locked state and an unlocked state by a lock member (40). The knob (44) of the lock member (40) has a reverse-tapered surface (445) gradually spreading in the direction of the outer peripheral part (413) of a dish-shaped member (41) toward the direction of the projection from the dish-shaped member (41). A user can easily catch the reverse-tapered surface (445) by his finger when the user lifts the cover body (30) to open it, whereby the lifting operation can be easily performed.