To perform a regeneration treatment without deteriorating fuel consumption regardless of accumulation of oil ash when DPF 12 for collecting PM is provided on an exhaust passage of an engine 1.

The amount of accumulated oil ash of DPF 12 is assumed based on a travel distance 17 of a vehicle. A pressure drop in DPF 12 is detected by a differential pressure sensor 16 and the detected value is compared with a regeneration determination value corrected based on the oil ash accumulation amount to determine a regeneration timing. When it is determined to be the timing, a regeneration process (lag of injection timing and post injection of a fuel injection valve 9, reduction of an opening of an intake throttle valve 7 and reduction in super charged pressure of a supercharge device 4) to raise an exhaust temperature on the upstream side of DPR 12 is performed to combust and remove PM collected in DPF 12. The more the oil ash accumulation amount is, the higher the regeneration treatment temperature to be controlled is.