To reduce a learning error small and the error of an injection amount used for each control parameter so as to provide accurate control by determining the error of the injection amount of an idling time based on outputs from various sensors or switches and forcibly executing N ranging and an air conditioner OFF.

An idling time correcting means 5 is provided for correcting an injecting time to be idling time objective rotation based on the outputs of a fuel injection amount calculating means 2, an idling state determining means 3 and various parameter inputting means 4. Then, the permission of learning of an injection amount error is determined 6 based on the outputs of various parameter inputting means 4. Then, an engine state is forcibly established 7 for executing an injection amount error learning condition based on the output of the determining means 6, and an injection amount predicted to be actual injection at this time is calculated 8. Then, an injection amount error is calculated 9 based on the outputs of the means 5, 7 and 8 and an injection amount for controlling a control parameter is calculated 10.