An internal combustion engine control device is provided which can accurately estimate intake pipe temperature behavior during transient time even in an internal combustion engine embedded with a variable valve or a turbocharger. The internal combustion engine control device estimates transient behavior of the intake pipe temperature, on the basis of a flow rate (dGafs/dt) of gas flowing into the intake pipe, a flow rate (dGcyl/dt) of gas flowing from the intake pipe, an intake pipe pressure Pin, and a temporal changing rate (dPin/dt) of the intake pipe pressure. The device performs knocking control during transient time, on the basis of the estimated transient behavior of the intake pipe temperature.