PURPOSE: To improve start and restart properties by reducing and compensating an amount of fuel at the time of start in accordance with the reduction of battery voltage.

CONSTITUTION: The number of PTC heater 14 in operation is determined based on a battery voltage before the start of cranking which is detected by a battery voltage detection device 19. The number of PTC heater 14 in operation is set in such a way that it is reduced in accordance with the reduction of battery voltage. When the battery is deteriorated and battery voltage is reduced, electrical load which the PTC heater 14 and a starter motor demand may exceed power supply capacity of the battery. Therefore, the rotating speed of cranking which is necessary for the start is ensured by suppressing power consumption of the PTC heater 14 at this time. Thus, start and restart properties are improved.