A wafer cassette is provided which has a multiplicity of shelves provided in one side thereof with a notch and placed at intervals to give rise to open spaces therebetween for insertion of a wafer, provides the open spaces in the recesses thereof with buffer members severally adapted to meet in collision with part of the outer periphery of a wafer, and allows the notches in the multiplicity of shelves jointly to form an empty space for extractably admitting the leading end part of a wafer conveyor. The wafer cassette of this invention permits wafers carried on the wafer conveyor to be sent out past the leading end part of the conveyor and inserted automatically into the empty spaces formed in the cassette for insertion of wafers and stowed in the cassette after collision against the buffer members when the leading end part of the wafer conveyor (the end part on the wafer discharging side) is inserted into the empty space mentioned above and then set operating. Thus, the accommodation of individual wafers and the conveyance of a cassette as an integral unit are simultaneously materialized and the wafer processing system can be automated up to the very end thereof.