Abstract The nonresonant microwave response observed in the ESR measurements of YBa 2Cu 3O 7−δ was studied as a function of various ESR parameters. Its nonresonant nature was confirmed by an experiment and a theoretical calculation of the ESR-transition probabilities for parallel and vertical microwave polarizations. Field modulation dependence revealed that it was composed of two components: one is proportional to the modulation amplitude ( H m) and has the same polarity upon the sweep reversal of DC magnetic field. The other is only observed during sweep. It has opposite polarity and is proportional to H m only in a narrow H m range. Their reference-phase dependences indicated that both components were mainly out-of-phase microwave responses. The theoretical analysis of these behaviors and the modulation scheme implied that the two components were microwave responses to the static and dynamic magnetizations trapped in the bulk and at intergranular Josephson junctions, respectively, providing a method for the separation of the two kinds of trapped magnetization.