1. A nonlinear distortion compensating circuit comprising: a power calculator for calculating a power value of an input signal; an operating point setting unit for calculating an apparent power value from temperature information, supplied from an external source, representative of the measured temperature of a power amplifier for amplifying the input signal and the power value calculated by said power calculator, based on a relationship, which has been given beforehand to said operating point setting unit, between input vs. output characteristics of the power amplifier and the temperature of the power amplifier; an inverse characteristics calculator for calculating an inversion of a nonlinear distortion caused by the power amplifier from inverse characteristics data, which have been given beforehand to said inverse characteristics calculator, about the nonlinear distortion caused by the power amplifier and the apparent power value calculated by said operating point setting unit; and a complex multiplier for adding the inversion calculated by said inverse characteristics calculator to said input signal.