An inter-main-apparatus interface device, characterized by: a control data interface provided between a first-standard main apparatus and a second-standard main apparatus (901-1, 901-2, 901-N) for letting a controller included in the second-standard main apparatus (901-1, 901-2, 901-N) operate on the basis of control data supplied from the first-standard main apparatus; and a content data interface provided between the first-standard main apparatus and the second-standard main apparatus (901-1, 901-2, 901-N) for enabling the second-standard main apparatus (901-1, 901-2, 901-N), as controlled by the controller operating on the basis of the control data supplied from the first-standard main apparatus, to demultiplex first multiplexed data with first content data and second content data multiplexed, the first content data being sent from a first base station connected to the first-standard main apparatus to a second base station connected to the second-standard main apparatus (901-1, 901-2, 901-N), the second content data being sent from a third base station connected to the first-standard main apparatus to a fourth base station connected to the second-standard main apparatus (901-1, 901-2, 901-N) and send the demultiplexed first content data and the demultiplexed second content data to the second base station and the fourth base station and to multiplex third content data and fourth content data and send second multiplexed data with the third content data and the fourth content data multiplexed to the first base station and the third base station, the third content data being sent from the second base station to the first base station, the fourth content data being sent from the fourth base station to the third base station. a control data interface provided between a first-standard main apparatus and a second-standard main apparatus (901-1, 901-2, 901-N) for letting a controller included in the second-standard main apparatus (901-1, 901-2, 901-N) operate on the basis of control data supplied from the first-standard main apparatus; and a content data interface provided between the first-standard main apparatus and the second-standard main apparatus (901-1, 901-2, 901-N) for enabling the second-standard main apparatus (901-1, 901-2, 901-N), as controlled by the controller operating on the basis of the control data supplied from the first-standard main apparatus, to demultiplex first multiplexed data with first content data and second content data multiplexed, the first content data being sent from a first base station connected to the first-standard main apparatus to a second base station connected to the second-standard main apparatus (901-1, 901-2, 901-N), the second content data being sent from a third base station connected to the first-standard main apparatus to a fourth base station connected to the second-standard main apparatus (901-1, 901-2, 901-N) and send the demultiplexed first content data and the demultiplexed second content data to the second base station and the fourth base station and to multiplex third content data and fourth content data and send second multiplexed data with the third content data and the fourth content data multiplexed to the first base station and the third base station, the third content data being sent from the second base station to the first base station, the fourth content data being sent from the fourth base station to the third base station.