An apparatus for storing sheets carrying images thereon and sequentially driven out of an image forming apparatus in consecutive bins thereof is disclosed. The apparatus includes a deflector for deflecting a sheet toward the inlet of a preselected bin and a plurality of cylindrical cams cooperating to open and close the inlet of the bin. The deflector and cams are interlocked to each other to operate at a relatively high speed. The apparatus is capable of surely inserting a sheet into the inlet of the bin and highly reliable and durable.