Nonvolatile memory device and operating method of the same

An operating method of a storage device comprising a nonvolatile memory device comprising a first memory stack and a second memory stack, and a memory controller coupled to control the nonvolatile memory device, the operating method includes determining a first read voltage level with which a first memory cell of the first memory stack is successfully read, and performing a read operation on a second memory cell of the second memory stack using a second read voltage determined based on the first read voltage level.