In this study, we performed a modeling for $K^{+}$ ion-exchanged diffused channel waveguide and waveguide-type optical coupler by Wentzel-Kramer-Brillouin(WKB) dispersion equation, normalized field distribution equation for mode and coupled mode theory, and examined the optical-power-dividing of the optical coupler fabricated by using the modeling condition. The optical-power-dividing was observed at the waveguide-type optical coupler with 3[.mu.m] line-width, 6[.mu.m] space between channel waveguides, and 3[mm] interaction length.h.