An optical variable attenuator 1 has a planar waveguide 2 and an actuator structure 3. The planar waveguide 2 is provided with an input optical waveguide core 4A for input of an optical signal, an output optical waveguide core 4B for outputting an optical signal from the optical waveguide core 4A, and an a movable mirror optical waveguide core 4C for guiding light that does not enter the optical waveguide core 4B, out of the optical signal from the optical waveguide core 4A. The actuator structure 3 has a movable mirror 7 for reflecting the optical signal emerging from the input optical waveguide core 4A, toward the output optical waveguide core 4B. A light receiving device 10 for receiving light passing the optical waveguide core 4C is provided at one end face of the planar waveguide 2.