PURPOSE: To correct accurately a dead time by counting pulses as many as pulses which are not counted by a main circuit during a specific time after a specific time.

CONSTITUTION: A counter 13 for dead time correction and a timer 14 for fixing the counting time of the counter 13 are provided, and the counter 13 is applied with the output of a fast discriminator 8 directly, so all pulses which arrives within the specific time set in the timer 14 are counted. The counted number of the counter 13 in count-up mode is applied to the +1 counter 7 of the main circuit and the +1 counter 7 counts pulses continuously until its counted number attains to the final counted number of the counter 13. Consequently, pulses as many as the arrival pulses are counted by the main counter 11 and accurate dead-time correction is made.