To start an engine by supplying start fuel for increasing amount of fuel at the start and prevent start fuel from being continuously supplied when start causes failure.

A solenoid valve 13 is provided in a start fuel supply passage for supplying start fuel for increasing amount of fuel at the start separately from a fuel supply passage for supplying usual fuel into an intake passage, a base of a transistor TR1 for controlling the solenoid valve is grounded through a thermistor 21, and resistance 22 for heater is arranged in the vicinity of the thermistor. When supply of start fuel at the start is required, the solenoid valve is opened and current is fed into the resistance for heater. When amount of heat generation of resistance is increased and resistance of the thermistor is reduced as time elapses, the transistor is turned off. If the start causes failure until the time, supply of start fuel exceeding it is prevented to prevent so-called "fogging".