PURPOSE: To uniform the intensity of a laser beam without transmitting the laser beam of a high output through an optical component by using the optical component utilizing reflection such as a division mirror and a total reflection mirror.

CONSTITUTION: The laser beam transmitting a concave lens 6 is reflected and split on the split mirror 7, and is changed to two laser beams (a), (b) centering about a symmetric axis. The laser beam (a) is made incident on a coupling mirror 10 after being reflected successively on the total reflection mirrors 8a, 9, and 8a three times. While, the laser beam (b) is made incident on the coupling mirror 10 after being successively reflected on the total reflection mirrors 8b, 9, and 8b three times similarly. The laser beams coupled on the coupling mirror 10 are made to be in a state where the beams a' and b' are superimposed, and those laser beams are outputted by transmitting a convex lens 11, and are changed to outgoing laser beams with a small divergent angle by the convex lens 11, and are changed to the laser beams with an almost uniform intensity distribution at the focal position of the convex lens 11.