measuring a reflectivity of a substrate peripheral structure before heating, the substrate peripheral structure being placed close to the wafer and being heated simultaneously with the wafer by a plurality of heat sources;

measuring a wafer reflectivity of the wafer before the heating;

calculating a wafer emissivity of the wafer from the wafer reflectivity;

measuring a wafer radiation intensity of radiation emitted from the wafer during the heating;

calculating a wafer temperature of the wafer from the wafer emissivity and the wafer radiation intensity;

calculating a target value of on-wafer optical intensity on the wafer so that the wafer temperature becomes a preset temperature;

calculating a target value of optical intensity on the substrate peripheral structure from a difference between the reflectivity of the substrate peripheral structure and the wafer reflectivity so that incident light being incident on the substrate peripheral structure and wafer incident light being incident on the wafer have an equal optical intensity;

calculating target values of heat source optical intensity for heating by the heat sources so that the target value of on-wafer optical intensity and the target value of optical intensity of the substrate peripheral structure are achieved;

calculating target values of heat source power so that the target values of heat source optical intensity are achieved; and

inputting the target values of heat source power to the plurality of heat sources and causing the heat sources to emit light.