An apparatus is provided to control injection of fuel into an engine with a combustion engine. The fuel is injected into the combustion chamber as a preliminary sub injection and a main injection following the preliminary sub injection. The preliminary sub injection repeats one or more times and is less in an amount of the fuel than the main injection. The apparatus comprises acquisition means and a control unit. The acquisition means acquires a parameter showing at least one of a state of an exhaust gas exhausted from the cylinder after the combustion of the fuel and a constituent of the exhaust gas. The control unit includes variably setting means for variably setting a mode of the preliminary sub injection depending on the parameter acquired by the acquisition means.