PURPOSE: To surely measure time between start time and end time of time measurement even if counting number of a counter is insufficient while at least either of the start time and the end time of the time measurement being an event occurrence time point, nearly matching with the rise or the fall of a clock signal at the time when a continuously occurring event time interval is measured.

CONSTITUTION: A counter 22 repeatedly counts a clock signal of a specified frequency which a clock generator 20 generates, and the counted value is stored in a memory 14. A sine wave generator 24 generates a sine wave wherein three times of a clock signal cycle is made one cycle, and a phase shift circuit 26 produces a cosine wave of the same cycle. A/D converters 28, 30 convert the amplitude of the sine and cosine waves into a digital value at the time of event occurrence, which is stored in the memory 14. A processing circuit 32 finds a difference of the counted value of the counter 22 at the time of neighboring event occurrence, and gets a time between the times of the neighboring event occurrences from a phase angle for the sine wave at the time of each event occurrence found from the output of the A/D converters 28, 30.