To transmit required data without omission by shutting the repeating transmission of data signal to the side of SCSI bus and opening the repeating transmission of data signal from the SCSI bus to a repeating transmission line when an I/O signal is received from the SCSI bus side during an information transfer phase.

When the I/O signal is received from the side of SCSI bus 2 at a bus repeating device 1 to which a control circuit for data signal belongs, the repeating transmission of data signal to the side of SCSI bus 2 is shut off, and the signal of control circuit 5 for I/O signal is made positive and turned into H level. As a result, the output of OR 2 is turned into H level, and a repeating gate AND 1 from an SCSI bus 3 to the repeating transmission line is opened. Thus, required data can be transmitted without omission and further, an oscillating phenomenon can be prevented.