A game server controls plural game machine groups including a collection of game machines, each of which is brought into a status enabling to start a game based on a thrown coin or a given credit number and is given a payout according to a result of the game. The game server includes a processing unit that judges whether a cumulative credit consumption of a predetermined game machine group reaches a predetermined upper limit, based on information about credit consumptions of the plural game machine groups. The game server also includes a communication interface that sends, when the processing unit judges that the cumulative credit consumption of the predetermined game machine group reaches the predetermined upper limit, a return signal for executing a return based on a predetermined return rate, to one game machine of the predetermined game machine group. The return is executed regardless of a game result.