Disclosed is a biped walking mobile system or apparatus, typically a biped walking robot, which achieves walk stability without altering a preestablished gait, namely path of movement for each of joint region, as well as a walk controller and a work control method therefor. The biped walking mobile apparatus, advantageously made as a humanoid robot with an upper body (11) as its main body having its head and a pair of hands, has in its lower part a pair of leg portions (13L, 13R) attached thereto so as to be each pivotally movable biaxially, each of the leg portions having a knee portion (12L, 12R) in its midway and a foot portion (14L, 14R) at its lower end, the foot portions being attached to its corresponding leg portion so as to be pivotally movable biaxially, and includes drive means associated with the leg, knee and foot portions for pivotally moving them, respectively, a gait former 8249 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 (30) for controlling respective driving actions of the drive means on the basis of the gait data, the walk controller including a ZMP compensator (32), the ZMP compensator including: a ZMP sensor (23L, 23R) for detecting ZMP for each the feet portions (14L, 14R), a ZMP converter (35) for computing a ZMP target value on the basis of the gait data from the gait former, and a ZMP compensating stage (36) for comparing the actual measurement value of ZMP detected by the ZMP sensor with the ZMP target value from the ZMP converter to modify the targeted angular velocity and acceleration in the gait data from the gait former and thereby to compensate or correct the ZMP target value. Thus, with the targeted angular path of movement in the gait data which remains unaltered when the ZMP target value is compensated, no case is there that the paths of movement of various parts of the mobile apparatus or robot such as its main body or legs come off those preestablished in the gait data Accordingly, even in case, e. g., a the biped mobile apparatus has its free foot landing positions unalterable such as in stepping-stones, or an obstacle needed to be stepped over or passed under, it an achieve walk control with certainty.