A memory device in which reliability of a clock signal is improved is provided. The memory device comprises a data module including a clock signal generator configured to receive an internal clock signal from a buffer, and to generate a first internal clock signal, a second internal clock signal, a third internal clock signal, and a fourth internal clock signal having different phases, on the basis of the internal clock signal, and a first data signal generator configured to generate a first data signal on the basis of first data and the first internal clock signal, generate a second data signal on the basis of second data and the second internal clock signal, generate a third data signal on the basis of third data and the third internal clock signal, and generate a fourth data signal on the basis of fourth data and the fourth internal clock signal.