To improve heat efficiency by outputting a control signal of a prescribed pulse width and less by a control means, finding out an invalid injection period when fuel is not injected from an injector, making current flow onto a coil in the injector during the invalid injection period, heating the injector, and then heating fuel directly.

When a temperature sensor signal is outputted from a catalyst temperature sensor 6 from a time when an internal combustion engine is stopped at the time of cooling engine so as to prevent a catalyst temperature from attaining a prescribed temperature, the injector heating signal of a prescribed pulse width and less for finding out an invalid injection period is outputted from a control means 8 per a prescribed time, and an injector 2 is heated. When the catalyst temperature attains the prescribed temperature, the output from the catalyst temperature sensor 6 is changed, the output of the injector heating signal of the injector 2 is stopped, and heating of the injector 2 is stopped. If the heating signal of the injector 2 is outputted per prescribed time, the output of the injector heating signal is stopped for a constant period after/ before injection.