Disclosed are a storage device including a memory controller and a method of operating the memory controller. A storage device according to the technical idea of the present disclosure includes a write buffer for storing write data that is not grouped into a transaction, a non-volatile memory device including a journal buffer where journal logs are stored, a volatile memory device for temporarily storing first metadata, and a memory controller for updating the first metadata to the second metadata based on the journal log stored after the start of the checkpoint among the journal logs stored in the journal buffer.