Abstract: This invention discloses a data transfer system comprising a data transfer apparatus for transmitting clock signals and binary serial data signals, a clock signal-transfer line connected to the data transfer apparatus, a data signal-transfer line connected to the data transfer apparatus, and at least one data receiving terminal unit connected to the clock signal-transfer line and data signal-transfer line, the data receiving terminal unit regarding the data signal transmitted from data transfer apparatus as a transfer start signal when it detects that the data signal transmitted at the time corresponding to the leading edge of the clock signal transmitted from the apparatus has the first logic level, and that the data signal transmitted at the time corresponding to the trailing edge of the same has the second logic level, also regarding the data signal as a transfer data signal when it detects that the data signal transmitted at the time corresponding to the leading edge of the clock signal has the same logic