A first flash heating is performed in which a flash lamp emits a first flashing light to a semiconductor wafer having been heated to a first preheating temperature equal to or lower than 650 degrees C. by a light emission from a halogen lamp so that the temperature of a surface of the semiconductor wafer reaches 1000 degrees C. or higher. Then, a second flash heating is performed in which a second flashing light is emitted to the semiconductor wafer having been further heated by a light emission of the halogen lamp. Performing the first flash heating can suppress diffusion of impurity in the subsequent second flash heating. In the second flash heating, the impurity is activated and introduced crystal defects are recovered.