A device capable of adhering to and moving along the surface of an object, comprising: the main casing comprising an outer casing and an inner casing; an outer sealing member mounted at the opening of the outer casing, part of which is caused to contact the surface of the object; an inner sealing member mounted at the opening of the inner casing, part of which is caused to contact the surface of the object; and a means for moving along the surface of the object while maintaining the distance between the main casing and the surface of the object at a certain distance; wherein the outer casing, the outer sealing member and the inner sealing member, together with the surface of the object, define Area I, and the inner casing and the inner sealing member, together with the surface of the object, define Area II; wherein the pressure of fluid in Area I is maintained at a lower level than the pressure of fluid surrounding the Device, and the pressure of fluid in Area II is maintained at a higher level than the pressure of fluid in Area I.