This disclosure concerns a waveform corrector comprising a first portion calculating an offset value of an intermediate value between a maximum value and a minimum value of a signal with respect to a reference value; a second portion calculating an actual amplitude of the signal by subtracting the offset value from the maximum value or the minimum value; a third portion generating a first correction signal by subtracting the offset value from the digital signal; a fourth portion subtracting a value obtained by shifting a figure of the actual amplitude from the actual amplitude so that the actual amplitude converges into a reference amplitude; and a fifth portion subtracting a value obtained by shifting the first correction signal by an amount identical to a shift amount of the actual amplitude from the first correction signal so that the first correction signal converges into a second correction signal.