An exhaust gas purifying apparatus includes a primary diesel particulate filter provided in an exhaust line of a diesel engine, a secondary exhaust line branched from the exhaust line at an upstream side of the primary diesel particulate filter, a secondary diesel particulate filter provided in the secondary exhaust line, and a low pressure part provided in the secondary exhaust line at a downstream side of said secondary diesel particulate filter. The secondary diesel particulate filter has a soot load capacity smaller than the soot load capacity of the primary diesel particulate filter. The low pressure part provides a pressure lower than a pressure of the branching point. The apparatus further includes a differential pressure measuring part for measuring a differential pressure between an inlet and an outlet of the secondary diesel particulate filter.