PURPOSE: To eliminate a scratch and to finish polishing with an extremely high accuracy in a short time, by composing a polishing tank used for the work machine device of a barrel polishing machine, etc., so that the length becomes more than 1.3 times as long as the diameter.

CONSTITUTION: Rotation is given with the body 2 to be worked and a polishing member 3 being input into a polishing tank 1 whose length L is made more than 1.3 times as long as its diameter . A precise polishing finish is thus completed in a short time without any gouge nor generation of scratch, because of the rubbing, superposing, colliding, etc., of the body 2 to be worked each other having gone.