Many conventional robots consisting of rigid frames and active joints have been controlled based on the information regarding collision avoidance in human environments. When these robots collide with a human, he/she can be seriously injured if their sensor systems have a defect or the power supplies are shut down. So, we have developed a human friendly robot that consists of two arms, a body, and a mobile base. It is covered by an air cushion bag which simulates the skin of a human. In this paper, its waist is described, which consists of pitch, roll, and yaw axes. Also, a passive collision force suppression mechanism that is installed in each joints of the human friendly robot is proposed. The passive collision force suppression mechanism consists of two fixed and linear guides, two compression springs, a release system, and a disk damper. When a collision between the robot and the environment occurs, collision/constant forces are first suppressed by the air cushion bag. If a larger collision force is exerted on the robot, the suppression mechanisms will become passively activated and the joints of the waist will disconnect. The robot, moreover, is capable of returning to a desired task by using the suppression mechanisms if the environment is cleared. Through collision experiments, the effectiveness of the waist mechanism and the suppression mechanism is verified.