PURPOSE: To economize time and cost required for maintenance or repair for software error by identifying the software error in an error report.

CONSTITUTION: When one bit error is detected from a data group 10 with check bit and an auxiliary information signal 11 such as an address or the like, an error detection report circuit 1 outputs an error information group 12 and an error report signal 13. An error information history circuit 2 stores the error information group 12 from the error detection report circuit 1 and successively outputs the contents as historical error information group 14. An error information comparator circuit 3 compares the error information group 12 from the error detection report circuit 1 and the historical error information group 14 from the error information history circuit 2 and outputs a match signal 15 when those groups are matched.