Disclosed is a waveguide type optical device utilizing a nonlinear refractive index change according to a large 3.sup.rd order nonlinear optical phenomenon. The waveguide type optical device includes a signal beam waveguide through which a signal beam propagates; and a pump beam waveguide through which a pump beam propagates, wherein the pump beam waveguide is disposed adjacent to the signal beam waveguide so that the pump beam can be coupled to the signal beam waveguide, the signal beam waveguide is made of nonlinear optical materials with large 3.sup.rd order nonlinear optical property and the pump beam waveguide is made of linear optical materials, and the wavelength range of the signal beam is different from that of the pump beam. By such a structure, the pump beam is coupled to one arm of the signal beam waveguide, thereby generating a 3.sup.rd nonlinear phenomenon on one arm of the waveguide through which the signal beam passes. Therefore, the waveguide optical device which implements an all-optical communication device operating as an optical device and can be integrated is provided.