The present invention provide an optical circuit device having: an optical circuit; a polarization beam splitter/combiner for splitting an incoming light beam into two polarization beams and combining the two polarization beams into an outgoing light beam; a first optical waveguide and a second optical waveguide for connecting the optical circuit and the polarization beam splitter/combiner and receiving the two polarization beams independently; and a polarization rotator, arranged on the first optical waveguide, for rotating a polarization plane of one of the two polarization beams split by the polarization beam splitter/combiner so as to match a polarization plane of the other of the two polarization beams, the optical circuit, the polarization beam splitter/combiner, the first optical waveguide, the second optical waveguide and the polarization rotator being integrated on a planar substrate.