To stably obtain a resonant radio wave absorber with a high yield capable of ensuring a radio wave absorbing performance at the time of a product inspection process in use.

During manufacturing before the product inspection process of the resonant radio wave absorber, after flushing condensation-type silicon resin obtained by mixing radio wave loss agent and curing agent on a conductive layer on which a silicon coat is formed beforehand, a thickness is controlled by a roller, a press machine or the like, and the silicon coat on the conductive layer and a silicon absorptive resin layer are reacted and stuck by a curing reaction of the resin.