First and second pairs of input/output lines transfer mutually complementary data signals respectively. First and second selection circuits select a signal transfer line having the same potential as that of a signal transfer line not precedently selected from two precedently selected signal transfer lines among first to third signal transfer lines and the signal transfer line not precedently selected and connect first ends thereof to the first pair of input/output lines respectively while connecting second ends thereof to the second pair of input/output lines respectively. Thus, no precharging may be performed for equalizing the potentials of the two signal transfer lines selected for present data transfer with each other, and hence reduction of a data transfer rate can be prevented.