PURPOSE: To irradiate an irradiating part with a laser beam by concentrating attention by releasing a laser beam cut-off means after detecting the fact that an operator catches a holding part at the terminal edge of a light introducing member.

CONSTITUTION: When an operator catches a handpiece 3, a detection signal supplied from a detecting means 11 is transmitted to a control circuit 10, which allows a beam 8 to retreat from the laser beam L. When an operator holds the handpiece 3 towards a laser beam irradiation object, e.g. eye 20, and contacts the detecting means 11, the control circuit 10 instructs a driving part 9 to retreat the beam stop 8. Therefore, the laser beam L is collected to the incidence edge of an optical fiber 4 by a condenser lens 7, and irradiated to the diseased part of the eye 20 through the optical fiber 4. When irradiation terminates, the contact with the detecting means 11 is suspended, and then the beam stop 8 cuts off the laser beam L.