To provide an optical circulator having an optical crystal part suitable for an optical system having little number of components and whose aligning is easy.

Two sheets of walk-off crystal polarizers are placed in series in the direction of an optical path, and two sheets of non-reciprocal polarization plane rotors are placed between the two sheets of walk-off crystal polarizers. Four sheets of reciprocal polarization plane rotors are placed between the two sheets of non-reciprocal polarization plane rotors. The four sheets form two sets, and each one set consists of the two sheets juxtaposed in parallel to the optical path. The two sets of reciprocal polarization plane rotors are placed in series in the direction of the optical path. Then, the optical crystal part of the optical circulator is constituted by placing a third sheet of walk-off crystal polarizer and a polarized wave dispersion compensator between the two sets of reciprocal polarization plane rotors. Besides, an optical system which combines ports consists of one lens, two-core TEC fiber and one-core fiber.