PURPOSE: To make possible a continuous cleaning work with a barrel being rotated again following the completion of a polishing work by, after finishing the polishing work, fitting on the opening of the barrel a porous lid, which is equipped with a rotary joint for connection of a cleaning pipe, in place of the closed type lid.

CONSTITUTION: At the time when the polishing work is completed, a closed type lid 22 used in the polishing work is taken off and a porous lid 23 for cleaning use is fitted on an opening 21a by use of a binder 9, and a sleeve 28 is properly held, through a stand 28a, on the extended member protruding from an internal frame 2. Next, a cleaning pipe 29 is connected to the sleeve 28, and the centering of the porous lid 23, a packing cylinder 27, and the sleeve is ckecked by rotating a barrel 1 and a cleaning fluid is supplied from the cleaning pipe 29 continuously or intermittently in accordance with the conditions. In this way, the cleaning fluid is supplied while rotating the barrel 1 with a proper control, and therefore it can be perfectly cleaned in a short time with a comparatively small amount of cleaning fluid. Additionally, the used cleaning fluid flows through a wire net 26 and drops down, and is led into the draining trench from a hopper 80.