A nonvolatile memory device includes a first memory chip and a second memory chip connected to a controller through the same channel. The first memory chip generates a first signal from a first internal clock signal based on a clock signal received from the controller. The second memory chip generates a second signal from a second internal clock signal based on the clock signal, and performs a phase calibration operation on the second signal on the basis of a phase of the first signal by delaying the second internal clock signal based on a phase difference between the first and second signals.