The present invention relates to an exhaust gas purifying apparatus comprising; a plasma-assist PM purifying reactor; a detecting device for detecting an amount of PM accumulated in the PM purifying reactor; a power supply for the PM purifying reactor; and a controlling device for controlling the power supply on the basis of signals from the detecting device. The controlling device controls the power supply to start supplying the electric power to the PM purifying reactor, or to increase the amount of electric power which is supplied to the PM purifying reactor, when the amount of accumulated PM detected by the detecting device exceeds a predetermined amount.