To provide a time measuring circuit capable of time measurement of a signal to be measured with higher accuracy than a resolution determined by a reference clock with a simple circuit and low power consumption.

This time measuring circuit for performing time measurement of a period when a pulse of the signal to be measured is in an active state is equipped with a self-running clock generation circuit for generating a self-running clock having a shorter cycle than a system clock having a known cycle, the first counter for counting the number of clocks of the self-running clock during the period when the pulse of the signal to be measured is in the active state and outputting the first counter value which is a counting result, and the second counter for counting the number of clocks of the self-running clock during a period of at least one cycle of the system clock and outputting the second counter value which is a counting result. The time of the pulse of the signal to be measured can be calculated from integration of the counter value by the first counter and the cycle of the self-running clock calculated from the counter value by the second counter.