A walk controller (30) for a biped (two-footed) walking mobile system, which drive-controls each joint drive motor (15L, 15R-20L, 20R) of each leg portion (13L, 13R) of a biped walking mobile system based on gait data, includes a force detector (23L, 23R) to detect the force allied to a sole of each foot portion (14L, 14R), and a compensator (32) to modify the gait data from a gait former (24) based on the force detected by a force detector, and is constituted so that each force detector (23L, 23R) comprises at least three 3-axial force sensors (36a, 36b, 36c) allocated on a sole of each foot portion (14L, 14R), and a compensator (32) modifies gait data based on the detected signals from three 3-axial force sensors (36a, 36b, 36c) which detect effective force, thereby the walk stability of a robot is realized, even on the unstable road surface condition with complex roughness.