To provide a supporting device which has a high freedom degree of selecting a mounting position in spite of a simple structure.

The supporting device 1 for supporting a tool on an object is provided with a means on a frame 2 for fixing the frame 2 and the supporting device 1 on the object. The tool is mounted to the supporting device 1. The supporting device 1 supports itself to the object. The frame 2 is provided with an upper support claw 3 and a lower support claw 4 which are effective even in the arrangement inclined to the object. The frame 2 including the upper/lower support claws 3, 4 forms a C-shape. The upper/lower support claws 3, 4 are designed in such a manner that the holding effect when the load is applied to the supporting device 1 is generated to a part of the object between the two support claws 3, 4 by the inclination of the two support claws 3, 4.