PURPOSE: To lower the concentration of nitrogen oxide in exhaust gas when exhaust gas generated from various kinds of combustion engines is purified by making fine particles, such as soot in exhaust gas be negatively charged by a charging mesh part, making it be adsorbed on a purifying filter part to collect it and further adding a denitrifying filter part.

CONSTITUTION: Inside an exhaust gas discharge route (exhaust pipe), a charge mesh part 210, a purifying filter part 220 and a denitrifying filter part 230 are arranged in this order of being nearer to a combustion engine. The charge mesh part 210 and the purifying filter part 230 are installed through insulating supporting bodies 214 and 222 and connected to negative and positive electrodes of a power source 216 respectively. Soot in exhaust gas discharged from the combustion engine is made be negatively charged in the charge mesh part 210 and adsorbed in the purifying filter part 220. The concentration of nitrogen oxide in the exhaust gas is lowered in a denitrifying filter part 230.