In a base station which has a plurality of antennas, each of a plurality of comparison circuits operates to compare correlation levels, which are obtained by despreading received signals for a plurality of channels, with each other with respect to the antennas. Each of a plurality of transmission antenna selecting circuits operates to determine from which antenna a transmission signal is to be transmitted for every channel. Each of a plurality of multiplexing circuits operates to multiplex the transmission signals of the individual channels, which are spread, for every antenna. As a result, on the basis of the result of the comparison of the correlation levels with respect to the antennas, a transmission antenna is selected for every channel, and the signals of the channels that are to be transmitted by a given antenna are multiplexed, whereby the base station achieves transmission diversity.