When it is determined that the combustion state during the catalyst warm-up control is unstable, an additional ignition is performed on the TDC side relative to the discharge period CP. In a first countermeasure example, an additional ignition period CP2 is provided on the TDC side relative to the ignition period CP1 at the normal time while performing normal ignition and injection. A second countermeasure example is carried out when it is determined that the combustion state is still unstable despite the first countermeasure example. In the second countermeasure example, an additional ignition period CP3 which is a longer period than the additional ignition period CP2 is provided instead of the additional ignition period CP2.