A susceptor that holds a semiconductor wafer placed thereon is capable of moving up and down inside a chamber. For preheating with a halogen lamp, the susceptor moves to a preheating position. The preheating position is a height of the susceptor that achieves the most uniform in-plane illumination distribution of light emitted from the halogen lamp and applied to the semiconductor wafer. After the preheating is finished, the susceptor moves to a flash heating position for irradiation with a flash from a flash lamp. The flash heating position is a height of the susceptor that achieves the most uniform in-plane illumination distribution of a flash emitted from the flash lamp and applied to the semiconductor wafer.