A semiconductor memory device includes a shared transistor controlling coupling between a bit line pair in a memory cell array and a bit line pair in a sense amplifier. After a word line is activated and the sense amplifier amplifies the potential difference between the bit lines of the bit line pair in the sense amplifier, the shared transistor is tuned OFF and precharge/equalizing circuit is activated to precharge the bit lines in the sense amplifier to a potential which is half the internal power source potential.