A signal processing apparatus includes a recording unit, an operation unit, a processing unit and an abnormality detector. The recording unit records configuration data therein. The operation unit performs arithmetic and logical operations on an input signal and outputs an operation signal indicative of the result of the operations. The operation unit has a circuit configuration defined by the configuration data recorded in the recording unit. The processing unit acquires the operation signal outputted from the operation unit, produces an output signal based on the acquired operation signal and outputs the produced output signal. The abnormality detector detects an abnormality of the circuit configuration of the operation unit. Moreover, in the signal processing apparatus, the processing unit is configured to further acquire an abnormality detection result from the abnormality detector after the acquisition of the operation signal and output the output signal depending on the abnormality detection result.