A clock converting circuit (1) receives and then converts m-phase clocks of a frequency f having a phase difference of 1/(f×m) to n-phase clocks of the frequency f having a phase difference of 1/(f×n). A single-phase clock generating circuit (2) receives the n-phase clocks of the frequency f having a phase difference equivalent time of 1/(f×n) to generate single-phase clocks in synchronism with the rising or falling edges of the n-phase clocks. Since the frequency of the m-phase clocks inputted to the clock converting circuit (1) is ‘f’, if a desired frequency of the single-phase clocks is decided, then ‘n’ can be obtained from the equation: the frequency of the single-phase clocks is equal to (f×n). This value of ‘n’ is set to the clock converting circuit (1), thereby obtaining the n-phase clocks of the frequency f from the m-phase clocks of the frequency f to provide single-phase clocks of a desired frequency.