The present invention serves to prevent inequity among game arcades by effectively using the communication band of a communication line in a game arcade in which a game device for an online game is located. When a game device in a location A and a game device in a location B play an online game via an external network, the master terminal device is determined based on the master priorities Mp of both devices. The master priority is calculated in accordance with the status of each location. A formula for calculating the master priority is set so as to balance the number of master terminal devices with the number of client terminal devices in a location, and/or so as to effectively use the communication band of a communication line in a location.