A data storage device includes a nonvolatile memory device; a buffer memory for storing temporarily data to be transmitted from the nonvolatile memory device to a host device or data to be transmitted from the host device to the nonvolatile memory device; a memory control unit for performing a control operation for controlling the nonvolatile memory device; and a direct memory access (DMA) unit for performing a data transmission operation associated with the buffer memory, according to control of the memory control unit, wherein the DMA block transmits a first data from the nonvolatile memory device to the buffer memory, and wherein the DMA unit transmits a second data from the nonvolatile memory device to the buffer memory, while the first data stored in the buffer memory is transmitted from the buffer memory to the host device.