Abstract: A CAT temperature sensor which detects the temperature of a catalyst (catalyst temperature TCAT) is provided in an exhaust purification apparatus of an exhaust pipe, and an exhaust vent temperature sensor which detects the temperature of an exhaust vent (exhaust vent TEND) is provided in near the exhaust vent. A FIECU, in the case where the catalyst temperature TCAT is above a predetermined temperature TCAT1, or in the case where a temperature difference ?T obtained by subtracting the catalyst temperature TCAT from the exhaust vent temperature TEND is above a predetermined temperature difference ?T1, sets the flag value of a flooding determination flag F_INUN to “1”, and sets the flag value of an idle rotation speed increase flag F_INEUP which indicates that a target engine speed in the idle operating state of the internal combustion engine is increased by a predetermined rotation speed, to “1”.