A data transmission system (10) is provided with a transmission unit (1), a receiving unit (2), transmission paths (3), and a delay unit (4). The delay unit (4) is disposed on a transmission path (31) along which a high-speed signal (S1) is transmitted, and delays the transmission of the high-speed signal (S1) with respect to a low-speed signal (S2). When the high-speed signal is transmitted from a section b2 to c along the transmission path (31), a delay time of Delta(t) occurs with respect to when the high-speed signal is transmitted from a section a to b1 along the transmission path (31). In other words, the phase of the high-speed signal transmitted from section b2 to c is shifted with respect to the phase of the high-speed signal transmitted from section a to b1. Consequently, a time interval in which an EMI peak value occurs can be reduced, thereby enabling the probability of an EMI peak value occurring to be reduced.