An exhaust gas purifying device for an engine includes a particulate filter midway in an exhaust passage for collecting particulate matters. A control means calculates an accumulating amount of particulate matters on the particulate filter. An accumulating amount calculating means calculates the accumulating amount in accordance with an accumulating characteristic and differential pressure of the particulate filter detected using a differential pressure detecting means. When the accumulating amount becomes a predetermined regeneration demand amount, the control means performs a forcible regeneration, in which particulate matters on the particulate filter are burned and removed to regenerate the particulate filter.