In order to develop a method for the nondestructive evaluation of material deterioration in nuclear pressure vessels, changes in the electromagnetic properties of the low-alloy steel A533B, Class. 1 and its weld metal caused by neutron irradiation up to ∼3x10²³ n/m² of neutron fluence at 561K were measured. Electrical resistance, coercivity and Barkhausen noise were selected as the electromagnetic properties to measure. It was found that decreases of several % in the readings of electrical resistance and coercivity, and an increase of several % in the Barkhausen noise occurred due to neutron irradiation. Good correlations between the changes in the electromagnetic properties and those in the mechanical properties were confirmed. Furthermore, an equation using the results of the three tests was found to estimate well the transition temperature and yield strength. From this, the authors conclude that the electromagnetic tests have potential as methods for nondestructive evaluation of material deterioration in the reactor vessels of nuclear power plants.