To provide a high-frequency electric power detection apparatus, for precisely performing transmission output control at a wireless base station facilities or the like used for a CDMA wireless communications system, which reduces the influence due to variations in the characteristics of circuit elements and in the time constant in the detection of a peak value of a transmission signal and to obtain the peak value with high precision.

A multiphase rectifier 1-11 separates an inputted high-frequency signal into a plurality of signals having different phases by a phase shifter, inputs each signal having different phases into parallel-connected rectifiers, respectively, to rectify it, and combines the output signal of each rectifier and outputs it. The multiphase rectifier 1-11, having about six-phases or more, constitutes an average value detector 1-1. An output signal of the average value detector 1-1 is converted into a digital signal by an A/D converter 1-2, to be outputted as a peak value. Using the multiphase rectifier eliminates the need for a smoothing circuit, since the average value and the peak value become nearly the same value, thereby eliminating the influence due to the time constant of the smoothing circuit and reducing the influence of variations in the characteristics of circuit elements or the like.