The present invention provides an optical switch for making part of incident light, which has been made incident on an optical waveguide, selectively emergent to a light emergence portion provided outside the optical waveguide. The optical switch includes a liquid crystal device for selective emergence of the incident light. An arbitrary layer of the liquid crystal device is set such that letting &Dgr;n be a difference between a refractive index n0 of the optical waveguide and a refractive index n1 of the arbitrary layer of the liquid crystal device, “d” be a thickness of the arbitrary layer, and &lgr; be a wavelength of the incident light, the values of &Dgr;n, “d”, and &lgr; satisfy a condition of 2.20×10−3≦|&Dgr;n·d·&lgr;−1|≦3.03×10−3. With this optical switch, the uniformity of a light emergence efficiency can be easily realized by making use of a small change region in which the light emergence efficiency is not largely varied. The present invention also provides a display unit using the optical switches.