A control system for a mobile robot is provided with a base body 53 and a plurality of link mechanisms 52 and 54 connected thereto. A sensor 90 for detecting external forces is provided on a predetermined portion (knee) between the base body 53 and a distal portion (foot) 58 of the link mechanism (leg) 52. In a motion posture in which a robot 61 has a predetermined portion (knee) in contact with the ground, the displacement of at least a joint 55 between the base body 53 and the predetermined portion (knee) is controlled so as to bring an external force (floor reaction force) detected by the sensor 90 close to a desired external force. In a state wherein a portion other than a distal portion of a leg or arm of the robot 61 is in contact with a floor or the like and subject to an external force, the external force acting on the portion other than the distal portion of the leg or arm is properly controlled, thereby maintaining a stable posture of the robot 61.