PURPOSE: To effectively install a small-sized low polishing machine of compact structure by polishing balls while raising the balls and abrasives by a spiral body.

CONSTITUTION: A polishing pipe 2 is formed nearly to a U-shaped form seen from sides in which upper and lower corner parts 1a, 1b are rounded, and on the upper top side turning sideways of the polishing pipe 2, a motor 3 for driving a spiral body 1 is continuously provided sideways, an upper tank 4 is continuously provided below its upper top side, and a filter 5 possible to drop abrasives is provided on the lower surface side from the round part of the upper corner part 2 to the horizontal direction. Thus, the polishing device can be made into compact structure so as not to be elevated so much upward of a land where pachinko game machines are installed in one group and large-sized.