An optical switch has an optical waveguide whose output path of an optical signal branches into two, a carrier injection section which is provided to a branch portion of the optical waveguide and to which carriers are injected, and a refractive index change section which is provided to a optical waveguide layer of the optical waveguide and in which a refractive index changes in a case that carrier are injected to the carrier injection section, wherein the refractive index change section includes a quantum well layer.