PROBLEM TO BE SOLVED: To execute appropriate mixed simultaneous irradiation according to special light observation and treatment, etc.SOLUTION: In an optical path of broadband light BB emitted from a xenon lamp 30, a first D mirror 32, a diaphragm 33, a second D mirror 36 and a condenser lens 37 are arranged in order. An LD 31 for special light observation for emitting blue narrow band light Bn toward the first D mirror 32 is provided. An LD 35 for PDT for emitting treatment light Rn toward the second D mirror 36 is provided. During a special observation mode, the first D mirror 32 is inserted into the optical path, and the second D mirror 36 is withdrawn from the optical path. During PDT, the second D mirror 36 is inserted into the optical path, and the first D mirror 32 is withdrawn from the optical path. Since the blue narrow band light Bn is mixed with the broadband light BB on the upstream side of the diaphragm 33, the light quantity ratio of both of the light is kept fixed at a low cost. Since the treatment light Rn is mixed with the broadband light BB near a light guide 41, the decline of power of the treatment light Rn is suppressed.
