To provide technologies that can execute a variable probability upgrading presentation as previously intended after termination of a jackpot game.

If a 14-round normal jackpot or 14-round variable probability jackpot 2 [F2], or 14-round variable probability jackpots 3-6 [F7] are won in a normal state [F1], a 14-round jackpot game [F3] is executed, and the play enters a heart zone [F4]. The heart zone [F4] is a chance zone limited to four times of variation after termination of a jackpot game, and the variable probability upgrading presentation is executed in the zone. As the play is controlled in a special variation state in the heart zone [F4] even if a variation time reducing function is operated, the variable probability upgrading presentation as previously intended can be executed. If a player succeeds in the variable probability upgrading presentation in the heart zone [F4], the play enters a fireworks mode [F8] which is a variable probability mode. If the player fails in the variable probability upgrading presentation in the heart zone [F4], the play enters a beach mode [F5] which is a time reduction mode.