1. A biped walking mobile system, comprising: a main body having in its lower part a pair of leg portions attached thereto so as to be each pivotally movable biaxially, each of the leg portions having a knee portion in its midway and a foot portion at its lower end, the foot portions being attached to its corresponding leg portion so as to be pivotally movable biaxially, drive means associated with said leg, knee and foot portions for pivotally moving them, respectively, a gait former responsive to a demand for motion for forming gait data including data for a target angular path, data for a targeted angular velocity and data for a targeted angular acceleration, and a walk controller for controlling respective driving actions of said drive means on the basis of said gait data, said walk controller including a ZMP compensator, characterized in that said ZMP compensator includes: a ZMP sensor for detecting ZMP for each of said foot portions, a ZMP converter for computing a ZMP target value on the basis of the gait data from said gait former, and a ZMP compensating stage for comparing an actual measurement value of ZMP detected by said ZMP sensor with the ZMP target value from said ZMP converter to modify the targeted angular velocity and acceleration in the gait data from said gait former and thereby to compensate or correct said ZMP target value.