A volatile memory device includes: a first sense amplifier connected to a first memory cell through a first bit line, and configured to sense 2-bit data stored in the first memory cell; a second sense amplifier connected to a second memory cell through a second bit line, and configured to sense 2-bit data stored in the second memory cell, the second bit line having a length greater than a length of the first bit line; and a driving voltage supply circuit configured to supply a first driving voltage to the first sense amplifier, and supply a second driving voltage to the second sense amplifier, the second driving voltage having a voltage level different from a voltage level of the first driving voltage.