The Error Correction Code (ECC) circuit generates the first syndrome of write data, which have not been written to the memory. The Error Detection Code (EDC) circuit generates the second syndrome of verification read data, which have been written to the memory. The EDC circuit detects errors due only to the “read disturb phenomenon” using the second syndrome, the errors occurring in data scanned from the memory. The ECC circuit detects and corrects errors due to the “program disturb phenomenon” and the “read disturb phenomenon” using the first syndrome, the errors occurring in the data in which the errors due only to the “read disturb phenomenon” have been detected. As a result, both the circuit size and the processing time can be reduced.