Provided is a thermo-optic optical switch including an input waveguide configured to receive an optical signal, an output waveguide configured to output the optical signal, branch waveguides branching from the input waveguide to be connected to the output waveguide, and heater electrodes disposed on the branch waveguides and configured to heat the branch waveguides, wherein the branch waveguides includes first and second phase shifters having first and second thermo-optic coefficients of opposite signs.