Abstract: In the semiconductor manufacturing apparatus according to the present invention, there are provided a cassette stocker for accommodating wafer cassettes loaded with wafers, a reaction furnace provided with heating means, a reaction gas introducing means for introducing reaction gas into the reaction furnace, a gas discharging means for discharging exhaust gas in the reaction furnace, a boat for supporting wafers, a buffer cassette stocker for storing unprocessed wafers, a boat elevating means for inserting the boat into and retrieving the boat from the reaction furnace, a wafer transfer means for transferring wafers between the boat and the wafer cassette accommodated on the cassette stocker, and a wafer cassette transfer means for transferring wafer cassettes between the buffer cassette stocker and the cassette stocker, and the buffer cassette stocker is enclosed to provide an antioxidation area to prevent natural oxidation of the wafers in standby status.