PURPOSE: To improve drift correction accuracy of a tilt sensor by obtaining an interference angle obtained by assuming no action by compliance, and obtaining estimated floor reaction force from the interference angle so as to correct a sensor output in accordance with a difference from actual floor reac tion force, in an angle between a floor surface supposed by target walk capacity and the actual floor surface.

CONSTITUTION: An estimated tilt of a virtual plane including an tread estimated location is obtained by kinematic calculation from a robot attitude tilt estimated value and an articulated displacement detection value, and an estimated interference angle is obtained from a supposed floor surface tilt. Next from this estimated interference angle, estimated floor reaction force moment about a reference action point is obtained, based on a compliance model. Actual reaction force moment about the same action point to a 6-axis force sensor detection value is obtained. Then from a difference between the estimated floor reaction force moment and actual floor reaction force moment, a correction value is calculated from a correction rule, to correct a tilt sensor output.