To provide an exhaust gas purifying device capable of treating exhaust gas by applying a high voltage and performing stable discharge at a low voltage.

A purifying vessel 10 is constituted of an arc-like part 10a and a straight part 10b (non-arc-like part). An effective area of the purifying vessel 10 is enlarged by an area of the straight part 10b when compared with a cylindrical device. Consequently, treatment capability is increased without elongating a distance between electrodes 10 and 20. Since the shortest distance from the purifying vessel 10 in a cross section crossing the direction of exhaust orthogonally is constant in the internal electrode 20, the eccentricity of a discharge path is suppressed.