An exhaust emission purifier includes a catalyst unit disposed in an exhaust pipe of an engine. Electrodes (reaction adjustment unit) are provided on a honeycomb carrier of the catalyst unit in a layered form in order to apply an electric field to the vicinity of the catalyst surface to thereby adjust the catalytic reaction. An ECU serves as a status detection unit to detect factors which affect the exhaust gas purifying performance of the catalyst unit (i.e., operating conditions), and serves as a control unit which controls the electric field applied by the electrodes, on the basis of the detected operating conditions.