Transmission output detectors extract transmission outputs of a plurality of transmission branches, and an inter-branch error detector detects a combined signal level of the transmission outputs of the transmission branches to obtain an error detection signal. A correction controller calculates an amplitude error between the transmission branches based on an error detection signal, and calculates a phase error between the transmission branches based on an error detection signal which is obtained by changing the phases of the transmission branches. A phase controller and an amplitude controller correct the amplitude error and the phase error.