A 3D optical switch for transferring an optical signal between a plurality of layers of an optical integrated circuit, which comprises: a first optical coupler for distributing the optical signal input to a first optical waveguide deployed in a first layer among the plurality of layers to a second optical waveguide deployed in a second layer different from the first layer; a phase shifter for changing a phase of a first optical signal in the first optical waveguide passing through the first optical coupler and a phase of a second optical signal in the second optical waveguide distributed by the first optical coupler; and a second optical coupler for combining the first optical signal of which the phase is changed and the second optical signal of which the phase is changed is provided.