PURPOSE: To provide a surface treating device capable of easily coping with the surface of a treated object having various shapes such as a curved surface and efficiently treating it even when an obstacle exists between the device and treated object.

CONSTITUTION: A rotary shaft 2 is extended from above toward a nonmagnetic tube 1, and the lower end of the rotary shaft 2 is connected to a flexible rotary plate 13. Multiple magnets 4 are dispersively fitted to the lower face of the rotary plate 3. A regulating plate 5 is arranged above the rotary plate 3. The regulating plate 5 is constituted of a flat plate section 5a penetrated by the rotary shaft 2 and slant plate sections 5b, 5c continuously formed at the prescribed angles on both sides of the flat plate section 5a. When the rotary shaft 2 is rotated by a motor, the rotary plate 3 is rotated, the outer periphery section of the rotary plate 3 is regulated downward by the slant plate sections 5b, 5c of the regulating plate 5, thus the rotary plate 3 is deformed and held at the shape along the inner face 1a of the nonmagnetic tube 1.