In a total internal reflection-type optical waveguide switch which comprises optical waveguides crossing each other so that a refractive index changing region for developing a reflective surface is formed at a crossing section between the waveguides, the refractive index changing region has a configuration such that the reflective surface constitutes a concave surface recessed with respect to one lateral portion of the crossing section. When the refractive index changing region is not activated, incident light upon the spot corresponding to the reflective surface is insensitive to changes of the refractive index in the refractive index changing region, so that the initial crosstalk level can be lowered.