A chamber has a wall surface fitted with a liner. The liner is removably provided to the chamber with no fixed relation therebetween. By simply opening a light source to remove a heat diffusion plate, a hot plate and a tubular member from the chamber, the liner can be easily detached accordingly from the chamber. When a semiconductor wafer cracks to litter the chamber with its fragments, the chamber can be easily cleaned by simply detaching the liner. The liner has an outer surface subjected to surface roughening by honing. When a flash lamp emits flashlight of considerably high intensity, the roughened outer surface of the liner serves to block this flashlight. As a result, the metal surface inside the chamber is prevented from being exposed to the flashlight emitted from the flash lamp.