An exhaust gas purification apparatus (20), comprising: a primary diesel particulate filter (22) provided in an exhaust duct (21) of a diesel engine (11); a branched secondary exhaust duct (21A) from said exhaust duct on an upstream side of said primary diesel particulate filter; a secondary diesel particulate filter (22A) provided in said secondary exhaust duct, said secondary diesel particulate filter having a capacity smaller than a capacity of said primary diesel particulate filter; and a differential pressure measuring part (22B) that measures a differential pressure between an inlet and an outlet of said secondary diesel particulate filter, so that a quantity of particle deposition in the primary diesel particulate matter is measured using the secondary diesel particulate filter.
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