PURPOSE: To allow continuous movement of a moving device by selectively position-controlling and adsorbing surface in the most pulling-in position away from an object surface, a standard position or the most extended position, in a device freely movable along the wall surface of such large structure as a hull etc., and the surface of a rock.

CONSTITUTION: Four sets of adsorbing units having each one of vacuum suction disks 51 to 54, are arranged in four rows in parallel with the ascending direction of a device. Each adsorbing unit is provided with a first linear actuator composed of two rodless cylinders 2. A second linear actuator is also provided by having two tandem cylinders 4 supported by one linking plate 3 for forming a linkage between the pistons of respective cylinders 2 and moved back and forth in a direction crossig an object surface 01 and the vacuum suction disks 51 to 54 are provided in the tip parts of respective piston rods via spherical bearings. The positions of the respective adsorbing disks 51 to 54 are controlled selectively so as to occupy the most pulling-in position, a standard position or the most extended position.