An optical switch includes: an input-output port with three or more ports arranged along a direction; a modulator that includes an incident layer, a reflective layer, and a modulation layer disposed between these layers, spatially modulates light entering the incident layer from any port of the input-output port, and outputs the light spatially-modulated toward any of other ports of the input-output port; and a condensing lens that optically couples the input-output port and the modulator, wherein x2≠2x1+x0 holds where: a coordinate axis is along the direction of the input-output port and an optical axis of the lens is set as an origin of the coordinate axis; x0, x1, and x2 respectively are coordinates of a first port to/from which light is input/output, and a second port and a third port from/to which light input to or output from the first port is output/input; and x1,x2>0.