The object of the present invention is to provide a waveform shaping device and an error measurement device which can perform a waveform shaping operation with the sufficient amplitude margin, even if the mark ratio of the inputted data signal is significantly varied and the amplitude of the inputted data signal is decreased. The waveform shaping device according to the present invention comprises a voltage detector (22) for detecting an inputted data signal (Da) to obtain an amplitude value and the center amplitude voltage of the inputted data signal (Da), a reference voltage generator (23) for generate the reference voltage corresponding to the center amplitude voltage, and a comparator (25) for comparing the inputted data signal (Da) with the reference voltage, and in which the waveform shaping device further comprises a correction information outputting section (27) for outputting correction information V on the basis of a mark ratio (M) and an amplitude of the inputted data signal (Da), the correction information V used to correct the center amplitude voltage detected by the voltage detector (22), and a correction section (28) correct the reference voltage or the inputted data signal to be inputted to the comparator (25) on the basis of the correction information (V).