A plurality of balls inserted in the gap space between an outer ring raceway surface and an inner ring raceway surface are arranged at equally spaced intervals in a circumferential direction. The procedure of this ball arranging method for a ball bearing includes a ball holding step of holding any ball in the gap space by a ball holding mechanism provided at a tip of a robot arm and a ball moving step of moving the ball held by the ball holding mechanism along a pitch circle, and these steps are repeatedly performed for the plurality of balls based on a control program. Accordingly, the plurality of balls are arranged at equally spaced intervals on the pitch circle.