A transmission system for transmitting a transmission signal, includes a section for outputting a periodic clock having a preset period, a section for transmitting the transmission signal in synchronism with the periodic clock, and a section for receiving the transmission signal transmitted from the transmitting section. The receiving section includes a section for generating a data synchronizing clock synchronized with variation of values of sampling data, section for detecting a phase difference between the periodic clock and the data synchronizing clock, and a section for generating a phase variable clock obtained by varying phase of the periodic clock so that a variable phase difference which is a phase difference between the phase variable clock and the data synchronizing clock becomes an amount set in advance.