PURPOSE: To detect the abnormality of a processing task other than a WDT (watchdog timer) task, and to take an appropriate measure against the abnormality in respect of a digital processor provided with a software self-diagnostic function.

CONSTITUTION: In the digital processor provided with the software self- diagnostic function provided with an abnormality occurrence monitoring task 6 to execute the clearing processing of the counter 4 of an abnormality occurrence monitoring means 2 within monitoring time and the processing task 8, a holding means 10 to receive the operating state reporting information of the processing task 8 and a judging means 12 to judge whether the operating state reporting information received by the holding means 10 shows the normality of a digiatal processing task or not are provided, and the counter 4 is cleared at the time of the judgement of the normality, and the counter 4 is not cleared at the time of the judgement of the abnormality.