A first encoding part encodes a reference timing determined by a reference clock by using a delay line. A second encoding part encodes a measurement start timing and a measurement end timing of a measurement period determined by a measurement signal to be measured by also using the delay line. A count part counts the reference clocks included in the measurement period. A fraction calculation part calculates a start fraction number indicating a time difference from the measurement start timing and an immediately-following reference timing and an end fraction number indicating a time difference from the measurement end timing to an immediately-following reference timing, based on the encoding result. The fraction calculation part then calculates a fraction data indicating a difference between the measurement period and a product of the period of the reference timing and the count value of the count part.