PURPOSE: To measure a pulse signal at a high count rate by providing a signal processing means generating a pulse signal being the result of subtraction of an output of a delay line from an output of a differentiation circuit.

CONSTITUTION: An output signal 52 of a preamplifier 51 is fed to a CR differentiation circuit with P/Z (pole zero) canceller and its output signal 54 is fed to a delay line waveform shaping circuit 55. Then an output signal 54 is fed to a noninverting input of the amplifier 56 constituting the delay line waveform shaping circuit 55, while a signal 59 delayed by τd and attenuated by a prescribed rate through the delay line 58 is inputted to an inverting input. That is, the amplifier 56 is used to subtract the negative signal 59 from the positive output signal 54 to obtain a signal 61. Thus, the part of the attenuated waveform is removed to extract only the pulse width τd thereby attaining the high count rate measurement of the pulse signal.