A storage controller communicates with an external device including a submission queue and a completion queue. An operation method of the storage controller includes receiving a notification associated with a command from the external device, based on a first clock, fetching the command from the submission queue, based on a second clock, performing an operation corresponding to the fetched command, based on a third clock, writing completion information to the completion queue, based on a fourth clock, and transmitting an interrupt signal to the external device, based on a fifth clock. Each of the first clock to the fifth clock is selectively activated depending on each operation phase.