A memory device includes a memory cell array having a plurality of memory cell groups with a corresponding plurality of independent channels, and the device and an operating method thereof perform an internal data processing operation for the memory cell groups. The memory device includes an internal command generator configured to generate one or more internal commands in order to perform an internal data processing operation in response to a reception of a command, and an internal common bus for a common internal processing channel which is disposed to be shared by the plurality of memory cell groups and configured to form a transmission path of data between the plurality of memory cell groups when the internal data processing operation is performed.