To provide a medical laser beam irradiator for allowing not only an operator but also a third person to minutely and accurately observe a treatment state at treatment time.

This laser beam irradiator has an optical fiber 3 for emitting a laser beam from the tip by making the laser beam from a laser beam supply means incident from the rear end, a hand piece 1 for holding this optical fiber 1, a light input surface 21 integrated with this hand piece 1, and facing to at least a laser beam irradiating area, an imaging means 20 for imaging or picturing at least the laser beam irradiating area on the basis of the light received via this light input surface 21, a display device 30 for displaying an imaging result by this imaging means 20, and injection means 40, 40A, 41, and 42 for jetting in front of the light input surface 21.