This paper reviews the present status of GaN-based power devices which has started the practical applications. Normally-off characteristics were realized by introducing p-type AlGaN gate structure, where holes are injected into the channel reducing the on-resistance by conductivity modulation. Experimentally fabricated GaN GIT inverter system attained the world-highest conversion efficiency over 99.3% by using bilateral structure. AlGaN/GaN Natural Super Junction was also developed to overcome the trade-off between the blocking voltage and the on-resistance. Further, a fusion of microwave and power devices was developed as Drive-by-Microwave technology. Finally, direct liquid-immersion package technology, where GaN chip are mounted inside the heat-pipe, was demonstrated. The technology contributes to the dramatic reduction of junction temperature, which had been a problem caused by the increased power density of GaN devices.