A data storage device includes a magnetic layer having a plurality of magnetic domains, a write head provided at an end portion of the magnetic layer, a read head to read data written to the magnetic layer, and a current controller connected to the write head and the read head. A method of operating the data storage device includes reading data of an end portion of the magnetic layer using a read head provided at the end portion of the magnetic layer in which a write head is provided at the other end portion thereof, moving a magnetic domain wall of the magnetic layer by a distance corresponding to the length of one magnetic domain toward the end portion, and writing the read data to the other end portion of the magnetic layer using the write head and a current controller provided between the write head and the read head.