Annular reflecting rings are removably mounted on the upper and lower sides of a chamber side portion of a chamber. An annular recessed portion is formed sandwiched between the lower end face of the upper reflecting ring and the upper end face of the lower reflecting ring to surround a holding part for holding a semiconductor wafer. The outer peripheral surface of the recessed portion communicates with a transport opening. The formation of the recessed portion prevents the light emitted from halogen lamps and flash lamps from being non-uniformly reflected around the holding part to enter a semiconductor wafer, thus improving the uniformity of the in-plane temperature distribution in the semiconductor wafer during heat treatment.