A repeater having different input and output frequencies converts a signal received with the input frequency to a first intermediate frequency signal based on a local oscillating frequency for intermediate frequency conversion, and converts the first intermediate frequency signal to a second intermediate frequency signal by performing digital processing on the first intermediate frequency signal. Then, the repeater generates a first frequency tone signal that corresponds to a difference between the input and output frequencies, and generates a second frequency tone signal from the local oscillating frequency for intermediate frequency conversion and the first frequency tone signal. The repeater up-converts the second intermediate frequency signal to the output frequency based on the second frequency tone signal, and transmits the signal.