According to a game system, the communication period between a radio controller serving as a slave and a game device serving as a master can be made variable in a power saving mode. In a scene which requires a certain real-time level, the communication period is shortened, while in a scene which does not require a certain real-time level, the communication period is elongated. This variability of communication period as appropriate in the power saving mode can reduce power consumption without degrading the game characteristic.