Provided is a technique for preventing damage to wafers and transferring means during the transfer of heated wafers, and increasing the number of processable wafers per unit of time. The apparatus for processing wafers according to one embodiment of the present invention comprises: a preheating device which receives a plurality of wafers transferred for heat treatment, and heats the wafers up to a preliminary temperature; a heat-treatment device which receives the plurality of wafers heated by the preheating device, and heat-treats the wafers up to a treatment temperature; and a preliminary cooling device which receives the plurality of wafers heat-treated by the heat-treatment device, and cools the wafers to a temperature lower than the preliminary temperature. The wafers are stored in a boat, and the wafer heat-treatment process is performed while the boat is circulating through the preheating device, heat-treatment device, and preliminary cooling device.