1. A multiprocessor system having a plurality of processors to which processors control to be performed is allocated, comprising: an abnormal operation detecting unit which detects an abnormal operation that has occurred in a specific processor of the plural processors; an instructing unit which instructs to change specific control allocated to the specific processor to be performed in a substitute processor which is one of the processors other than the specific processor based on a result detected by the abnormal operation detecting unit; and an abnormal operation diagnosing unit which diagnoses whether the abnormal operation occurs in hardware of the specific processor; wherein when the abnormal operation is detected in the specific processor by the abnormal operation detecting unit, the specific control is performed by the substitute processor instructed by the instructing unit; and when the abnormal operation is diagnosed to be not in the hardware of the specific processor by the abnormal operation diagnosing unit after the abnormal operation detecting unit has detected the abnormal operation of the specific processor, previous control which has been allocated to the substitute processor before the specific control is allocated to the substitute processor is performed by the specific processor by being allocated to the specific processor.