The invention relates to an inner-carrier interference removing device and method, capable of suppressing the inner-carrier interference due to the transmission path character time change using the relative less computational amount. A delay spectrum estimation part estimates the delay spectrum of the transmission path to obtain the delay spectrum (DP1) as the estimation result according to the known signal in the receiving signal (RS). A delay part delays the delay spectrum (DP1) by preset time and outputs the delay signal (DeltaDP1). An amplitude/phase change amount calculation part compares the delay spectrum (DP1) with the delay signal (DeltaDP1) and calculates the time change amount of the amplitude and the phase direct towards each incoming wave(main wave and delay wave). A first window function calculation part calculates the window function w(k) based on the time change amount of the amplitude and the phase direct towards the incoming wave. A window function multiplying part multiplies the window function w(k) output by the first window function calculation part with the effective symbol in the receiving signal (RS) and outputs the multiplied receiving signal (MRS).