[Problem] To improve operator convenience in controlling the ON/OFF states of a plurality of wireless speakers. [Solution] A wireless speaker 1, when instructed through a power button or by a controller 2 to transition to an ON state, causes said wireless speaker 1 itself to transition to an ON state and also transmits a command for ON state transition to each of other wireless speakers 1 belonging to the same group as said wireless speaker 1. When instructed to transition to an OFF state, said wireless speaker 1 transmits a command for OFF state transition to each of the other wireless speakers 1 belonging to the same group as said wireless speaker 1, and also transitions to the OFF state. If an ON state transition command has been received from another wireless speaker 1, then the wireless speaker 1 transitions to the ON state, and if an OFF state transition command has been received, then the wireless speaker 1 transitions to the OFF state.