PURPOSE: To mirror-machine a work via barrel machining by sticking an abrasive on the inner peripheral face in a horizontal shaft type drum with the centrifugal force and stirring the work in this abrasive at the optimum speed to polish it.

CONSTITUTION: An abrasive G with the volume nearly a half of the inner volume of a drum 3 is put in the drum 3. A drum driving motor 10 is started to rotate the drum 3 at a high speed, thus the abrasive G is stuck to the inner peripheral face of the drum 3. A jig driving motor 16 is rotatively driven, the rotating speed of this motor 16 is controlled by a rotation control means 51, a work fixing shaft 43 is rotated at the preset rotating speed via a planetary gear mechanism by the drive of the motor 16. A work fixed and held by this work fixing shaft 43 is stirred in the drum 3 and mirror-machined by the abrasive G.