The present invention, in the multi-wavelength selector, and outputting M pieces of single-wavelength optical signals multi-wavelength light the multi-wavelength light sinhojung predetermined N number of single-wavelength optical signal inputs a signal in the direction of the entered call is the multi-wavelength optical signal consisting of the first waveguide; and one end of the N single-wavelength optical signals, each of the modulation period grating type for reflecting such that constructive interference at the one end to that connected with the first waveguide transmission spread the multi-wavelength optical signal in a plan view a second waveguide composed of the other end; and including, in the service of the condenser / focus multiple wavelength selection for selecting a plurality of single wavelength optical signal from the multi-wavelength optical signal needed without lens unit for converging the optical signal. Modulation period grating, waveguide