To prevent a player from losing the interest in a game, while maintaining reliability of a special performance to be executed over a plurality of variations.

When a newly acquired lottery element and a variation pattern determining element are stored upon occurrence of a lottery chance while a start condition is not satisfied, a result of an internal lottery and a variation pattern are decided in advance by using the newly acquired lottery element before consumption. A selection ratio of determining a prescribed special performance pattern is adjusted based on the decided variation pattern, as well as the execution history of special performances executed by a forecasting special performance execution means in a plurality of variable display performances.