To provide a time measuring apparatus by which the time can be measured at a high speed while its detecting resolution is kept at a definite level.

In addition to a circuit constitution for time detection, a constitution which is used to measure the cycle of measuring input pulses PIN is installed. As an initial processing operation, the output of a switch SW2 is supplied to the side of a counter C4, and the cycle of the measuring input pulses PIN is measured. On the basis of its result, a microcomputer MP1 changes over a switch SW1, and the frequency dividing ratio of the measuring input pulses PIN is changed. The switch SW2 is instructed to change over the output, and the time is measured.