To prevent a situation allowing some players to benefit and make all players equally enjoy a game in connection with an increase or a decrease in points obtained by paying a monetary value.

Information concerning points (expenditure history BP) that a player paid in the past and points (income history PP) that the player received in the past is recorded in a player information database in association with the ID of the player. In a game of the player, and an actual payment rate PP/BP is computed from the expenditure history BP and the income history PP, and the actual payment rate and a previously fixed set payment rate P/B are compared. As the result of the comparison, the kind of a gem is determined to a player whose actual payment rate is lower than the set payment rate on the basis of an occurrence rate B in which the probability of selection of a kind of a gem that increases points. An increase or decrease in points, therefor, can be controlled for each player.