A sheet feeding unit includes a supporting member configured to rotatably support a rotary feeding member, a first retaining member configured to push the supporting member upward from the underside to retain the rotary feeding member at a waiting position, and a second retaining member protruding on the underside of the supporting member when the first retaining member retains the supporting member. The retention of the supporting member by the first retaining member is released in association with the mounting of a sheet storage portion in the mounting position, and then the retention of the supporting member by the second retaining member is released.