PURPOSE: To obtain a data output without leak-out of data and delay time difference between forward and backward data transmissions by connecting bi-directional data flip-flop circuits with lateral symmetrical through a transmission gate.

CONSTITUTION: A latching means 26 and another latch means 27 of the same constitution are connected through a transmission gate 11. And a control signal is generated from a forward/backward changeover signal and a clock signal, and with the control of the transmission gates(TG) 5, 9 and 7 of the means 26 and 27 by the generated signal, TG 11 is made conductive with a slight delay compared with TG 7. By this method, the data transmission from the means 26 to means 27 or from means 27 to means 26 is slightly delayed and the output to the data input terminals 3 or 1 is also slightly delayed. Thus, leak-out phenomenon of data can be prevented.