An operation method of a MRAM of the present invention stores in memory arrays, error correction codes, each of which comprises of symbols, each of which comprises bits, and to which an error correction is possible in units of symbols. In the operation method, the symbols are read by using the reference cells different from each other. Moreover, when a correctable error is detected in a read data of the error correction code from data cells corresponding to an input address, (A) a data in the data cell corresponding to an error bit is corrected, for a first error symbol as an error pattern of one bit, and (B) a data in the reference cell that is used to read a second error symbol is corrected for a second error symbol as en error pattern of the bits.