A magnetic disk controller includes an error check code generating unit that generates error check codes associated with the encoded pieces of writing data; a first buffer that stores a first encoded piece of writing data and a first error check code associated with the first encoded piece; a second buffer that stores a second encoded piece of writing data and a second error check code associated with the second encoded piece; and a buffer control unit that, in a first period, substantially concurrently with a writing of the first encoded piece and the first error check code from the first buffer into a first sector of the magnetic disk, stores the second encoded piece and the second error check code into the second buffer.