PURPOSE: To make it easy to travel on a wall surface horizontally and vertically by equipping four legs fitted with negative pressure suckers, a releasing means of the suckers for release the suckers from a wall surface, and an open and close means of the legs for adjusting the distance between the suckers which is adjacent to each other.
CONSTITUTION: At the first stage, cylinders 20 to 23 for telescopic motions of the first to the fourth legs and the cylinders 61 and 62 for open and close motions of the first and second legs are set in elongated state, while the first to the fourth suckers 24 to 27 are set in sucking state by cylinders 28 to 31 for sucking, and the fifth sucker 32 is set in sucking state by a cylinder for sucking. For instance, according to the order to travel upward, the first and the fourth suckers 24 and 27 are set in released state, and the cylinders 20 and 23 for telescopic motions of the first and fourth legs, and the cylinders 61 and 62 for open and close motions of the first and the fourth legs are set in contracted state respectively. Then, the first and the fourth suckers 24 and 27 are set in sucking state, the fifth sucker 32 is set in released state, and the cylinders 20 and 23 for telescopic motions of the first and the fourth legs are set in elongated state. Thereafter, the fifth sucker 32 is set in sucking state, the second and the third suckers 25 and 26 are set in released state, and the cylinders 21 and 22 for telescopic motions of the second and the third legs as well as the cylinders 61 and 62 for open and close motions of the first and second legs are set in elongated state, and then the second and the third suckers 25 and 26 are set in sucking state.