PURPOSE: To execute coincidence of laser beams in a short time by multiplexing each of two or more laser beams by a direction correcting means which is capable of moving them two-dimensionally, and irradiating it to a pinhole through a lens of positive power.

CONSTITUTION: Laser beams 1a, 2a are emitted from two laser light emitting devices 1, 2, respectively, and as for the laser beam 1a of them, the direction is corrected by the first direction correcting means 4, and thereafter, the direction is changed by a mirror 6, and said beam is made incident to a polarized beam splitter 7 functioning as an optical multiplexing means. On the other hand, the laser beam 2a is a P wave when it is emitted from the laser light emitting device 2, but it is changed to an S wave by a 1/2 wavelength plate 3, made incident to the polarized beam splitter 7 after its direction has been corrected by the second direction correcting means 5, and the two laser beams 1a, 2a are multiplexed by this polarized beam splitter 7.