To provide a technology that can eliminate a noise fluctuated for a wide period and superimposed on a reference clock signal.

This noise-eliminating device is provided with a frequency-generating means, that generates a frequency of a recovered clock signal on the basis of a control signal, a comparison means that compares a phase of an input clock signal with a phase of the recovered clock signal and provides an output of a signal with a level depending on the result of comparison, a filter means that eliminates a high-frequency components from the signal outputted from the comparison means, a detection means that detects a fluctuation range of the signal whose high-frequency components are eliminated by the filter means, a comparison means that compares whether the fluctuation width detected by the detection means is the prescribed fluctuation width or larger, and a control signal generating means that calculates the mean value of the fluctuation width detected by the detection means when the result of the comparison by the comparison means denotes that the fluctuation width detected by the detection means is the prescribed fluctuation width or larger and generates the control signal, by which the recovered clock signal resulting from eliminating the noise from the input clock signal can be generated on the basis of the calculated means value.