A base station device of the present invention includes a base-station main body connected to a network, and multiple antenna units connected in series to the base-station main body. The base-station main body multiplexes signals acquired from the network and outputs the multiplexed signals to an antenna unit. The antenna unit demultiplexes the multiplexed signals into a signal to be transmitted by the antenna unit and another signals to be transmitted by another antenna unit, and transmits the other signal to the other antenna unit. The antenna unit multiplexes a signal received by the antenna unit and a signal received by the other antenna unit, and outputs the multiplexed signals to the base-station main body. The base-station main body demultiplexes the multiplexed signals, and transmits the demultiplexed signals to the network. Each antenna unit includes a demultiplexer of a single-input and three-outputs and a multiplexer of three-inputs and a single-output.