PURPOSE: To obtain an inexpensive beam splitter device for a high-output laser which divides regular single-lateral-mode laser light into plural beams without using any partial transmission mirror and has high reliability and light resistance by dividing the laser light into numbers of laser beams through a total reflecting mirror.

CONSTITUTION: Regular high-output laser light 12(5') in single lateral mode such as TM01 emitted from a laser oscillator 1 travels straight as shown by an arrow 13 through a pipe-shaped optical path cover 4 to strike the small-sized total reflecting mirror 9 and is split into two at a wave trough, and the lower half part is reflected as shown by an arrow 14 and made incident on a condenser lens 8. The upper half part, on the other hand, is reflected by a total reflecting mirror 3 as shown by an arrow 16 to enter the condenser lens 8. Consequently, the beam splitter device for high-output laser light which attain plural-beam splitting without any expensive partial transmission mirror and has high reliability and light resistance is obtained.