This paper describes about a vertical movement climbing robot using worm gear. The worm gear has a characteristic that about two digit reduction ratio with one step and is not driven reversely to the drive side. Using this characteristic, we developed the robot which prevented a fall by reverse drive even if a motor stopped during going up and down. In this paper, we describe about a basic structure and mechanism of this robot. We carried out a climbing experiment and confirmed a validity of the structure and mechanism of the robot.