The present invention reduces the size of a power detection circuit. An RF power amplifier includes an RF amplifier circuit and a power detection circuit. The RF amplifier circuit subjects an RF input signal having a predetermined frequency band to power amplification and generates an RF amplifier output signal. The input terminal of the power detection circuit is coupled to the output of the RF amplifier circuit. The power detection circuit detects a harmonic component having a harmonic frequency that is a whole number multiple of the frequency of a fundamental wave component of the RF amplifier output signal, and generates at an output terminal a detected signal indicative of the signal level of the fundamental wave component of the RF amplifier output signal. The power detection circuit includes an input circuit, which detects the harmonic component, and an output circuit, which generates the detected signal at the output.