To provide a pulse counter which steps accurately corresponding to the duration of on-state of input signal.

The time when OFF→ON change of an input signal is detected by an OFF→ON detecting part 12 is stored in a time memory 15, the time difference between that time and the time when ON→OFF change is detected by an ON→OFF detecting part 13 is stored in a time difference storage memory 18. The number of pulses corresponding to the time difference is stored in an increment memory 22, and a pule count value corresponding to the number of pulses stored in the increment memory 22 is stored in a pulse counter memory 25 based on a specified pulse count rate. Thus, an accurate pulse count value corresponding to the duration of the on state of input signal is provided.