The paper describes a way of designing the gait for a biped robot, which is derived from falling down avoiding motion. Our proposed approach includes two phases of the motion, one is to remain standing at the spot, and the other is to take a step forward for avoiding the falling down. At first, the approach to remain standing at the spot is mentioned, where the COP on the ground should be made converge to the center of stable zone of the robot. The control method introducing the target COP is proposed in the approach. And then, the approach to take a step is described later, where the stepping motion is practically examined in many experiments and the regions of stable gaits are investigated among the pace, the foot velocity and the COG speed. Finally, the continuous walk is achieved with based on the falling down avoiding motion. The validity of the proposed approach is confirmed in several physical experiments.