It is made possible to detect degradation in a circuit before an operation fault will occur. A semiconductor integrated circuit includes: a circuit to be tested; a plurality of logical circuits which have different logical thresholds and which perform operation on an output of the circuit to be tested, on the basis of the logical thresholds; and a degradation notice signal generation circuit which generates a degradation notice signal to give notice that the circuit to be tested has degraded, when outputs of the logical circuits do not coincide with each other.