PURPOSE: To heighten the working efficiency, and reduce labor by carrying out polishing processing mechanically and automatically even if it is a curved surface such as stone.

CONSTITUTION: When a curved surface such as stone (w) is polished, a tool is installed on a robot arm 1 so as to be capable of advancing and retreating in the prescribed direction f1 as well as to be capable of rotary operation, and in a process to operate the robot arm 1 by a computer control device 2 to which a necessary program is inputted, the tool is advanced and retreated, and is pushed against a surface w1 to be processed under proper pressure, and is also moved along the surface w1 to be processed.