A duplexer module prevents a transmission signal and a reception signal in the same band from interfering with each other. The duplexer module includes a transmission line, a reception line, and an antenna common line. In addition, the duplexer module includes a plurality of mounting electrodes arranged along the four sides of an outer edge of a mounting surface of a multilayer substrate. The fourth mounting electrode defining a monitoring port is disposed on a side different from a side on which each of the first mounting electrode defining a transmission port, the second mounting electrode defining a reception port, and the third mounting electrode defining an antenna port is disposed. The fourth mounting electrode defining the monitoring port is a mounting electrode used to output a signal of the monitoring line through which a portion of electrical power is transmitted from the transmission line.