To detect whether test object moves, together with its direction of movement.

Two photosensor part 1A and 1B having moving parts 2A and 2B which move corresponding to the movement of a test object, four optical fibers 3A, 3B, 3C and 3D, and a transceiver part 4, are connected. Then, optical signal is emitted from the transceiver part 4 and the optical fiber 3A, and then the optical signal fed back from the optical fibers 3B and 3D is received with the transceiver part 4 for converting into electric signal, so that the sequence signal corresponding to the movement direction of the test object (or the moving parts 2A and 2B) is obtained.