Abstract: Two AWG circuits are integrated while preventing degradation in quality of a multiplexing/demultiplexing function. An arrayed waveguide grating circuit includes: a first slab waveguide (52) connected to a first input waveguide (51a) and second output waveguides (55b); a second slab waveguide (54) connected to first output waveguides (55a) and a second input waveguide (51b); and an array waveguide (53) connecting the first slab waveguide (52) and the second slab waveguide (54), wherein the input waveguides (51a, 51b) are connected to the slab waveguides (52, 54) at an interval of 1.5× from the outermost second output waveguide out of the second output waveguides (55a, 55b) connected at an interval x depending on a wavelength.