A method of controlling a biped walking robot to balance the robot based on a sensed ground reaction force. In the method, X and Y coordinates are assigned to positions of sensors attached to a sole of a leg of the robot and a corresponding Z coordinate is assigned for at least three of the sensors based on the sensed ground reaction force sensed by at the sensors, respectively. A ground reaction force plane is specified based on the sensed ground reaction force and a normal vector perpendicular to the ground reaction force plane is calculated. A roll angle about an X-axis and a pitch angle about a Y-axis are calculated and an actuator is driven in correspondence to the roll angle and the pitch angle to move a part of the robot to align the normal vector with a reference vector of the gravity direction.