PURPOSE: To prevent a wall surface moving robot from falling down by using a suction means.

CONSTITUTION: A pair of support frames 4 and 5 are connected in such a fashion that they may move relatively while an expandable driving leg equipped with a suction means to a wall surface 2 is installed to each of the support frames. In a state where either support frame is mounted to the wall surface 2 of a structure 1 with an attracting means of the expandable attracting leg, the other side-support frame is arranged to make a relative motion, thereby constituting a wall surface movable robot which may move along the wall surface by alternating the motion. Each of ropes 11, 14a and 14b of an upper winding-up device 9 installed to the upper part of the structure and a pair of lower winding-up devices 13a and 13b installed to the lower part of the structure is fixed and three-point-supported. Therefore, when dropping from the wall surface, the wall surface movable robot moving along the wall surface of a structure, such as a spherical gas holder for flaw detection, such as weld beads is protected and stabilized and protected as well by eliminating such pendulation or swing motions.