A memory controller includes a buffer memory including memory banks, one or more host access units configured to perform an access to the buffer memory for a host, one or more memory access units configured to perform an access to the buffer memory for a memory device, and a processor configured to control an operation of the memory controller. The processor divides the memory banks into an external memory bank group for an external operation related to the host, and an internal memory bank group for an internal operation within a memory system. The host access units access the external memory bank group. The memory access units access the external memory bank group to perform the external operation, and access the internal memory bank group to perform the internal operation.