To provide an apparatus for OFDM transmission capable of transmitting an OFDM signal without distortion, without using an expensive component or a complicated circuit constitution by lowering an instantaneous power to mean power ratio.

An OFDM transmission system supplies a signal IFFT- transformed by an IFFT unit 102 to a signal decision unit 103, and detects a predetermined instantaneous power of a first threshold or more and a predetermined instantaneous power of a second threshold. If the instantaneous power becoming the first threshold or more or the instantaneous power becoming the second threshold or less is detected, a subcarrier detector 104 obtains the subcarrier for increasing the instantaneous power and the subcarrier for decreasing the instantaneous power of the subcarriers for constituting the signal. The obtained subcarrier is shortened or elongated in its amplitude value by a primary modulator 101, and again IFFT-transformed by the IFFT unit 102.