A fuel injection device including an injector that injects fuel into a cylinder of an engine; a fuel injection amount obtaining unit that obtains a fuel injection amount of fuel injected by the injector; a heat generation amount obtaining unit that obtains a heat generation amount of the fuel injected by the injector and ignited; and a control unit that determines that injector abnormality occurs, when determining that a difference between a fuel injection amount obtained by the fuel injection amount obtaining unit and a reference fuel injection amount is within a predetermined range and that a heat generation amount obtained by the heat generation amount obtaining unit is greater than a reference heat generation amount corresponding to the reference fuel injection amount. Accordingly, whether or not injection hole corrosion occurs in the injector can be determined.