The robots realized at present, are primarily developed for automation in factory, such as industrial robots. Recently, intelligent robot with vision etc. appeared, but the object of introduction doesn't change, so much.New field of robot with more advanced functions is developing, whose object is inspection and maintenance of large plant such as nuclear generating facilities. But realization of this type of robot by present technology is very difficult, because it requires remote, mobile operation. It requires to solve many technical problems for development of advanced robot. Especially important problem for it, is locomotion technology of robot. There are crawler, wheel and rail transportation as the conventional locomotion techniques, but they have a peculiar drawback, that is lack of smoothness when there is obstacles in locomotion route.In these cases, multi-legs articulated mechanism is suited well. So that, development work is busy in worldwide.In this time, Hitachi developed and demonstrated “Biped Robot” for TSUKUBA EXPO'85 in Goverment Theme Pavillion, under the cooperation of prof. Kato of Waseda University.This articulated mechanism. realized highlevel autonomous two legs walk which simulates human walk by oil hydraulic technology. The features of this robot is that all components except electrical power source is mounted on robot trunk. That is, power supply, composed of oil pump and auxilliaries, controller, composed of microcomputer and amplifier etc. are all mounted on robot. As follows, details of the biped robot will be explained.