PURPOSE: To provide an optical switch in which distances between a body to be detected and a light emitting part, and between the body to be detected and a light receiving part are kept sufficient, whose constitution is simple, and whose operability is good.

CONSTITUTION: A laser diode 11, a power meter 12, a switch part 20 are mutually connected through an optical fiber 30 constituted of an optical fiber 31 for transmission, an optical fiber 32 for reception, and an optical fiber 33 for transmission and reception, and an optical branching/coupling device 34. The switch part 20 is constituted of a main body case to which the fiber 33 is connected and which receives outgoing light from the fiber 33, and plural reflectors having a lens condensing the outgoing light to be a light beam and a reflecting surface reflecting the light beam.