To suppress the exhaustion of untreated PMs to the outside while covering shortcomings of an electrostatic adsorption type device.

A flow path control valve 17 is used for selectively connecting a trapping reactor 10 at its exhaust side to a main exhaust passage 15 and a sub exhaust passage 16. The selection of the sub exhaust passage 16 and the use of a PM filter 20 suppress the exhaustion of the untreated PMs while filtering exhaust gas. The stop of adsorption by the trapping reactor 10 and the use of the flow path control valve 17 for connecting the trapping reactor 10 at its exhaust side to the sub exhaust passage 16 suppress the exhaustion of the PMs while separating the PMs and regenerating the electrostatic adsorption type trapping reactor 10 and these actions during low speed operation suppress pressure loss due to the filter type PM filter 20.