A memory device including a plurality of nonvolatile memory chips each including a status output pin and a buffer chip configured to receive a plurality of internal state signals, which indicate states of the plurality of nonvolatile memory chips, from the status output pins and output an external state signal having a set period on the basis of the internal state signals indicating a particular state, wherein in a first section of the external state signal having the set period, a duty cycle of the external state signal determines depending on an identification (ID) of the nonvolatile memory chip which outputs the internal state signal indicating the particular state among the plurality of nonvolatile memory chips.