The combustion heater when operates at a cold time increases a temperature of engine cooling water, and includes a combustion chamber in which the combustion takes place, an air supply passageway through which the air for the combustion is supplied to the combustion chamber, a heating plug for igniting a combustion fuel within the combustion chamber, and a combustion gas discharge passageway for discharging from the combustion chamber a combustion gas burned in the combustion chamber. Of the air supply passageway and the combustion gas discharge passageway, at least the combustion gas discharge passageway is connected to an intake passageway of the engine, through which the intake air flows toward the cylinders of the engine. The combustion heater has an air suction fan for regulating a quantity of air supplied to the combustion chamber via the air supply passageway, and an ECU which includes a CPU for controlling an operating state of the air suction fan according to an engine rotational speed.