A wavelength selective optical switch device includes an incidence and exit part where a signal beam made of light of a multiplicity of wavelengths enters and a signal beam of a selected wavelength exits, a wavelength dispersion element that spatially disperses a signal beam according to the wavelength thereof and multiplexes reflected light, a condensing element that condenses the light dispersed by the wavelength dispersion element onto a two-dimensional plane, and a wavelength selection element that uses a multilevel optical phased array arranged in a position to receive incident light developed on an xy-plane made of an x-axis direction and a y-axis direction perpendicular thereto developed according to a wavelength, having a multiplicity of pixels arrayed in a lattice on the xy-plane, and that cyclically changes the phase shift amount in the y-axis direction to a sawtooth wave pattern for each pixel on the x-axis.