A wavelength selective switch includes a substrate. On the substrate, the wavelength selective switch includes at least one input port, a dispersive element, a light converging element, a light deflecting member, an output port, and a driving mechanism which drives at least one of the dispersive element, the light condenser element, and the light deflecting member, and drive by the driving mechanism is a rotational drive around an axis perpendicular to the substrate, for the dispersive element, and is a translational drive in a direction of dispersion of wavelength with respect to the substrate, for the light condenser element or the light deflecting member.