Wrong-act-preventing-function installed game device, wrong-act-preventing method during playing game and its program

In a game device in which a plurality of players participate in a game, not less than the number of players set in the game device are prevented from wrongful participation in the game. The game device accepts setting of the number of players who participate in a game (the set number of players) and executes the game with the set number of players. During the play of the game the number of players participated in the game is detected. The game device compares the number of the players participated in the game with the set number of players and, if the former is over the latter, the game device changes the degree of difficulty in the game. If the degree of difficulty in the game is higher than the present, for instance, it makes them difficult in continuing the game, so that a period of time for a wrong act to continue can be shortened. Further, if the degree of difficulty in the game is lower than the present, it makes them less interested in continuing the game, so that a period of time for such a wrong act