An optical switch includes: a first birefringent element; a first Faraday rotator; a first half-wave plate; a second birefringent element; a second half-wave plate; a second Faraday rotator; and a third birefringent element, which are arranged in a forward direction from the front, wherein the first birefringent element splits light in the forward direction from a first optical port into ordinary and extraordinary lights emitted onto first and second optical paths, respectively, the first and second half-wave plates are arranged on the first and second optical paths, respectively, and in the first and second Faraday rotators, a permanent magnetic field in a left-right direction and an external magnetic field in a front-back direction in an on state are applied to a Faraday element, a bidirectional optical path is formed between the first and second optical ports in an off state, and the optical path is interrupted in the on state.