Device for estimating the intake air amount of an internal combustion engine

A correction unit corrects a previously computed amount of air passing through a throttle valve (6) based on a pressure differential between the atmospheric pressure and the previously computed intake pipe pressure when the intake pipe pressure is replaced by the atmospheric pressure. An intake pipe pressure calculation unit computes the intake pipe pressure downstream of the throttle valve based on the previously computed intake pipe pressure and previously computed amount of air passing through the throttle valve. An intake air amount calculation unit computes the amount of intake air based on the currently computed intake pipe pressure. A limitation unit replaces the currently computed intake pipe pressure with the atmospheric pressure when the currently computed intake pipe pressure is higher than the atmospheric pressure.