A magnetoresistive sensor including a lower electrode layer, a discontinuous structure film provided on the lower electrode layer, the discontinuous structure film being composed of an insulator matrix and a plurality of metal islands dispersively arranged in the insulator matrix, a magnetoresistive film provided on the discontinuous structure film, and an upper electrode layer provided on the magnetoresistive film. The discontinuous structure film is partially etched at a central region thereof to thereby make a conduction between the upper electrode layer and the lower electrode layer at the central region through the magnetoresistive film and the metal islands.