In a duplexer module, a transmitting signal is correctly monitored without deteriorating receiving sensitivity. The duplexer module includes a transmission line, a reception line, and an antenna common line, and performs conversion between a transmission signal and a reception signals and antenna common signals. A transmission filter is inserted into the transmission line, and the transmission filter allows the transmission signal to pass therethrough and stops the reception signal. A reception filter is inserted into the reception line, and the reception filter allows the reception signal to pass therethrough and stops the transmission signal. A first line of a coupler which detects the transmitting signal is inserted into the transmission line at a stage subsequent to the transmission filter.