To provide a memory array for information bit that stores information bits, a memory array for check bit that stores check bits, a correction circuit that, in response to a write request, reads the information bit and the check bit corresponding to a write address from the respective memory arrays and corrects an error included in the information bit, and a mixer temporarily holding information bit corrected by the correction circuit. The mixer overwrites only a part of bytes of the held information bits with write data according to a byte mask signal. Accordingly, a capacity required for the memory array for check bit can be reduced while the byte mask function is maintained.