A real time signal analyzer capable of generating time region data and frequency region data at substantially the same time, and resetting a central frequency and a signal analysis range, the analyzer being provided with frequency conversion means (14, 16) for frequency-shifting input time region data and carrying out a thinning-out operation, an FFT processor (18) adapted to FFT-compute output data from the frequency conversion means in real time, a delay means (28) for delaying the output data from the frequency conversion means, a means (32) for storing the frequency region data from the FFT processor, a means (36) for storing the time region delay data read out from the delay means, and means (30, 38) for feeding back the data read out from the time region data storage means, instead of the input time region data, to the frequency conversion means.