PURPOSE: To prevent the infiltration of dust at the time of removing a connector by providing a light guiding system with a mounting member and constituting the laser device in such a manner that a shielding mechanism installed in a body is driven by the mounting member, by which a laser beam is shielded.

CONSTITUTION: An argon laser beam coagulating device which is an intraocular photocoagulating device is used to photocoagulate the fundus oculi. The laser beam emitted from a laser oscillating section installed in the device body is reflected by a half mirror and is then made incident via a condenser lens 7 on the light guiding system from which the laser beam is sent up to a laser probe. The device has the shielding mechanism 10 having a sheet-like shutter 11 for shielding the laser beam and covering the condenser lens 7. A moving ring 19 is pulled in a direction D by a return spring 23 and is simultaneously upward by the effect of an inclined groove 20 and a pin 18 in the state of not mounting a connector and, therefore, the shutter 11 exists above the condenser lens 7 and the fall of dust, etc., onto the condenser lens 7 is prevented.