To perform filter reproduction treatment without wasting the energy of a battery, by predicting a proper ignition conduction time and air supply time in advance, and operating a filter reproduction treatment means according to the predicted time.

The external temperature and the operation conditions (operation load, operation time, and lapse time after stopping operation) of a generator 2 are stored in a memory in a vehicle control device 17 constantly, and a proper conduction time is predicted each time based on, for example, the external temperature at that time and the operation conditions of the generator 2 immediately before performing the regeneration treatment of a filter 7. Then, a combustion heater 8 and an air pump 10 are energized according to the prediction time. Then, a battery 18 cannot be consumed more than needed.