I‐Vcharacteristics due to quasiparticles are observed with electromagnetic radiations of 96 MHz and 12 GHz in In/Au/Pb–oxide–Pb/Au/Pb tunnel junctions. The situation is clearly understood with the equivalent circuit model where the Josephson junction is connected in parallel with a resistance and a capacitance. The behaviors of the quasiparticle current are well classified into two groups according to whether the ratio of the resistance and the capacitive impedance is larger than or smaller than unity.