Wide-band-gap semiconductors, such as gallium nitride (GaN) and silicon carbide (SiC), are expected to be used as materials for new switching devices with low loss and high switching speed. The authors have recently developed a GaN-based high-electron-mobility-transistor (HEMT) for application to power electronics. In this paper we present models of a GaN-based transistor and Schottky barrier diode (SBD) for a simulation program with integrated circuit emphasis (SPICE). The results of the SPICE simulation show that the static and dynamic characteristics of GaN- based devices are precisely simulated by the SPICE models. The application of a GaN-based device to a single-phase AC-AC direct converter results in a reduction of power loss of over 30% compared with a silicon-based one.