A wavelength selection switch that includes an optical component for adjusting an optical path with an image magnification of M that is provided between a second imaging position and a mirror array. Therefore, it is possible to provide a small wavelength selection optical switch with a short optical path length that is capable of reducing the focal length of each of a first lens and a second lens to 1/M while maintaining the structure of the spectral element, the fiber array, and the mirror array according to the related art. Since the optical path length is reduced, it is possible to reduce the number of reflecting mirrors used to convert an optical path and thus reduce the size of a housing. Therefore, it is possible to reduce manufacturing costs.