For reducing time required for error correction in an error correction device, data are transferred from a buffer memory not only to a syndrome calculator but also to an error detector at the same time, and until the syndrome calculator detects an error-containing code, the error detector performs error detection in parallel with the syndrome calculation done by the syndrome calculator. During error detection after the error corrector corrects the error, mid-term results of the error detection obtained before an error-containing code is detected are used. Consequently, it becomes unnecessary to transfer all data from the buffer memory to the error detector, thereby making execution of an error detection process possible at a halfway point.