After start-up of an internal combustion engine, a CPU divides a request injection amount, which is used to control the air-fuel ratio to a target value, into an amount of fuel injected by a port injection valve and an amount of fuel injected by a direct injection valve based on rotation speed and a load ratio. When the amount of fuel injected by the port injection valve changes from zero to greater than zero, the CPU decreases the actual fuel injection amount from the divided fuel injection amount then gradually increases to the divided fuel injection amount. When the amount of fuel injected by the port injection valve is gradually increased, the amount of fuel injected by the direct injection valve is increased from the divided fuel injection amount so that the request injection amount of fuel is injected by the port injection valve and the direct injection valve.