Beam splitter and laser marking apparatus

A beam splitter (1) is configured by assembling three triangular prisms (1a, 1b 1c) having bottom surfaces formed in shapes of right isosceles triangles. A film (2) is formed on side surfaces of the prisms (1a, 1c) that include the edges of each right isosceles triangle for separating incident light. With this construction, light (B1) striking the apex angle of the triangle is reflected as two beams (B2)and transmitted as one beam (B3) by the light separating surface. Hence, the light incident on the beam splitter is separated in three directions.