A polarization beam splitter according to an embodiment of the present invention is provided with: a demultiplexer (11); a multiplexer (14); a first arm waveguide (12) at least one part of which is formed by a rib type waveguide; and a second arm waveguide (13) at least part of which is formed by a channel type waveguide. The indexes of refraction for the first arm waveguide (12) and the second arm waveguide (13) are the same for input light with one of linearly polarized light components that are orthogonal to each other, and the first and second arm waveguides are formed at waveguide widths such that the change in the index of refraction is the same for changes in waveguide width. With the other linearly polarized light component, a phase difference arises between a first input light propagated by the first arm waveguide (12) and a second input light propagated by the second arm waveguide (13).