In a heat treatment apparatus, a holding part moves upwardly to receive a semiconductor wafer transported into a chamber and placed on support pins. The semiconductor wafer held in close proximity to a light-transmittable plate by the holding part is preheated by a hot plate, and is then flash-heated by a flash of light emitted from flash lamps. Thereafter, the holding part moves downwardly to transfer the semiconductor wafer to the support pins, and the semiconductor wafer is transported out of the chamber. Then, a new semiconductor wafer is transported into the chamber. The holding part is adapted to perform such a series of operations of moving upwardly and downwardly also when in a standby condition pending the transport of the first semiconductor wafer in a lot into the chamber.