Fuel injection control device and method for multi-fuel engine

A fuel injection control device for a multi-fuel engine will not make the catalyst generate damage even if the fuel alcohol concentration learning value has a deviation from the actual alcohol concentration. In a fuel injection amount controller (105), if the learning value stored in the storing part (103) is high concentration, the decrement corrector (105a) decreases and corrects the fuel injection amount until the achievement of revaluation of the learning value. A learning value reviewer (105b) reviews the learning value of E concentration based on the oxygen concentration while the corrector reduces the fuel injection amount. A switch judgement part (105c) judges whether the injection fuel has been switched from the fuel residual in the fuel piping (17) to the fuel in the fuel-tank. The fuel injection amount controller (105) performs decrement correction to the mapped fuel injection amount corresponding to the learning value if the learning value of E concentration is high and the engine load is high, wh