PURPOSE: To measure the time interval with a resolution of less than one several-th of a reference clock by connecting a plurality of unit delay elements in series, setting the entire delay time several times or more as large as the reference clock, providing a latch circuit for every element, and measuring the time interval from the transient position information of the data.

CONSTITUTION: A reference clock 71 is so set as to allow the relationships among a period time Tt, the delay time Td of a unit delay element 22n to satisfy Tt=K × Td+ΔT (K: integer number), and supplies the reference clock. A unit delay detector 20n latches the delay times of n pieces of elements 22a-22n. Accordingly, the entire delay time becomes Tdly=n × Td. An encoder 30 inputs latch signals 24Qa-24Qn from FF 24a-FF 24n, detects the rise and fall transient positions of the signals, converts it into a binary signal, and supplies it to a data recorder 40. An arithmetic processing part 44 determines Tdly>Tt × (Td/ΔT)=Tt× Q (Q: resolution magnification) from the data, and measures the time interval with the ΔT as the measuring resolution.