PURPOSE: To permit good polishing to be performed under a desired condition of polishing, by measuring pressing force to a polished workpiece by a polishing tool in this tool and adjusting this pressing force being based on the result of this measurement.

CONSTITUTION: Pressing force, applied by an air cylinder 8, is transmitted to a polishing tool 6 by a piston rod 12, and a polishing sheet 6b is pressed to a polished workpiece 4 by suitable force. Reaction force of this pressing force is detected by a pressure detecting means 6c and input to a controller 30. When this detected pressure is different from a predetermined value desired for polishing in a proper polishing position, a device outputs an adjusting instruction signal of valve opening from the controller 30 to a pressure servo valve 24 so as to obtain the pressure of air eliminating this difference of pressure. The device, which controls the pressure servo valve 24 by this signal setting the pressing force to the polished workpiece 4 by the polishing tool 6 to a value optimum for polishing, polishes the polished workpiece 4 to the desired surface roughness.