Optical modulator

It is possible to reduce the size of an optical modulator which makes polarized waves orthogonal to each other between light pulses corresponding to adjacent bits on a time axis. The optical modulator includes an optical waveguide element in which a first waveguide is formed obliquely to an outgoing end surface, and a second waveguide is formed obliquely to both the first waveguide and the outgoing end surface, a lens whichmakes parallel optical paths of first and second modulated light beams outgoing from the first and second waveguides, a phase delay element which applies a phase delay to at least one of the first and second modulated light beams, a polarization beam rotating unit which rotates at least one polarized wave of the first and second modulated light beams to make the polarized waves orthogonal to each other between the two modulated light beams, and a polarization beam combining element which combines the first and second modulated light beams whose polarized waves are made orthogonal to each other. The thickness of the phase delay element in a light propagation direction is set to a thickness at which light pulses of the first and second modulated light beams are bit-interleaved by a phase difference due to the phase delay element and a phase difference due to the polarization beam combining element.