PURPOSE: To efficiently lead reflected light into a photodetector without using an adhesive by providing a prescribed space between a prism and the photodetector.

CONSTITUTION: The laser light from a laser diode chip 14 of an optical pickup 30 of a copying element is reflected by a semiconductor film M1 of a prism 18 and is thrown to an optical disk or the like. The reflected light from the optical disk or the like is transmitted through the film M1 and is reflected by films M3 and M2 and is made incident on photodetectors 22 and 24. A prescribed gap is formed between the prism 18 and photodetectors 22 and 24 and the refractive index of this gap space is about one; and when the prism 18 is made of an optical member having a low refractive index, the critical angle which reflects disturbing light is obtained, and the optical pickup where only reflected light is efficiently led into photodetectors without using an adhesive is obtained.