To provide double accuracy without doubling the frequency of an input pulse number or doubling gate time in a counting device.

Two each of oscillation output are counted every time of the rise or fall of pulses by a counter 12. The correction signals of 0 or ±1 are generated so as to be equal to the number of times of the rise and the fall within a gate period by the logic value of the oscillation output at the point of time of the rise and fall of gate signals. Then, the count value of the counter 12 is corrected in a correction circuit 13. In such a manner, counting is performed with the double accuracy without doubling an oscillation frequency or the gate time.