A time interval measurement system, by which measurement of individual time interval with remarkably improved measurement accuracy is made possible with smaller circuit scale, comprises a high speed counter section, an adder section, and a control section. The high speed counter section includes a m-bit counter unit having a plurality of m-bit counters for obtaining an integer part of the time interval between a START signal and a STOP signal, a first 1-bit counter unit having a plurality of first 1-bit counters for obtaining an decimal part of the time interval, and a high frequency pulse generator circuit. The high frequency pulse generator circuit periodically generates a plurality of delayed signals at intervals of a unit delay time which is shorter than the cycle time of the clock signal, according to the input of the START signal to the high speed counter section, and supplies each of a plurality of counter stop signals according to the delayed signals to a corresponding m-bit counter in the m-bit counter unit and a corresponding first 1-bit counter in the first 1-bit counter unit.