This invention relates to a nonlinear degree measuring apparatus and method for a power amplifier, and a predistortion compensation apparatus. The nonlinear degree measuring apparatus comprises a delayer (304), for delaying inputted pilot frequency data; a subtracter (305), for subtracting, from the pilot frequency data delayed by the delayer, subsequently inputted pilot frequency data; a power calculating unit (306), for calculating an instantaneous power of an outputted signal from the subtracter (305); and an averager (307), for averaging the instantaneous power calculated by the power calculating unit (306) to obtain an averaged power.