To provide a transmitter wherein even in a case of sharing a detector circuit between or among a plurality of transmitting circuits, a high degree of detection accuracy can be achieved without increasing the signal power supplied to the detector circuit. In a transmitter including a detector circuit shared by transmitting circuits and that deal with signals of different frequency bands, a capacitor C1, which constitutes an RF coupler disposed on an output signal line of the transmitting circuit, is directly connected to the input terminal of the detector circuit, while series coils L1 and L2 are inserted between a capacitor C2, which makes up an RF coupler disposed on an output signal line of the transmitting circuit which deals with signals of a lower frequency band than the transmitting circuit, and the input terminal of the detector circuit.