Low-energy Ar⁺ ion irradiation has been applied to an Au/BiFeO₃/Pt capacitor structure before deposition of the Au top electrode. The irradiated thin film exhibits multilevel resistive switching (RS) without detrimental resistance degradation, which makes the intermediate resistance states more distinguishable, as compared with the nonirradiated thin film. The stabilization of resistance states after irradiation is discussed based on the analysis of the conduction mechanism during the RS, which was investigated by means of temperature-dependent current-voltage measurement from room temperature to 423 K.