PURPOSE: To realize a stabilized laser beam working by performing the regulation of the optical axis of laser beam with a light energy-electricity converting element provided for an ideal optical axis on the emitting route of a laser.

CONSTITUTION: A thermoelectric couple 15 is installed at the position 4 symmetrical for the ideal optical axis Ci of the inside of a conduit pipe 9 as a light energy-electricity converting element. These thermoelectric couples 15 receives a heat by the irradiation of laser beam LB and outputs the electromotive force proportional to the energy of the laser beam LB received from the heat as an electrical output. The electric output is inputted into a comparator and the differential signal obtained therein is inputted into amplifier. The signal of the amplifier controls the motor for controlling and corrects the situation of the axial direction of output mirror.