PURPOSE: To always accurately discharge a ball even when a memory value of a number of prize balls is destructed by a noise or the like by periodically rewriting the selected number of prize balls in a memory means and discharging the prize balls from a discharge mechanism corresponding to the memory value in accordance with the number of prize-winning balls.

CONSTITUTION: A prize ball is discharged from a discharge mechanism corresponding to a prize-winning ball detected by a prize ball detecting means, based on a memory value by periodically rewriting a number of prize balls, where the number are selected by a prize ball number-selecting means, in a prize ball number memory means by a memory holding means. Accordingly, a prize ball discharge accurate as set is always performed with no influence by a noise or the like. A prize ball discharging time is shortened by selectively discharging the prize ball, when it is a small number, from a plurality of discharge mechanisms by an alternately discharging control means and by divisionally discharging the prize ball, when it is a large number, from a plurality of the discharge mechanisms by a concurrently discharging control means.