An internal combustion engine control device applied to an internal combustion engine, the internal combustion engine control device comprising: an injector-temperature calculation unit that calculates an injector temperature based on a coil resistance value of an injector; an internal-combustion engine temperature calculation unit that calculates a temperature (L3, L4) of the internal combustion engine based on the injector temperature (Li); and an operating-state control unit that controls an operating state of the internal combustion engine based on the temperature (L3, L4) of the internal combustion engine calculated by the internal-combustion-engine temperature calculation unit, a cold/warmed-up state determination unit that determines whether the internal combustion engine is in a cold state or a warmed-up state; an ambient-temperature calculation unit that calculates an ambient temperature around the internal combustion engine control device; characterized in that the internal combustion engine control device further comprises a correction unit that corrects the temperature of the internal combustion engine calculated based on the injector temperature by a subtraction amount, when it is determined that the internal combustion engine is in the cold state and a difference between the injector temperature and the ambient temperature is equal to or larger than a first predetermined value, and the correction unit calculates an initial value of the subtraction amount based on a relative relation with respect to the difference between the injector temperature and the ambient temperature, and decreases the subtraction amount with a passage of time since start-up of the internal combustion engine. an injector-temperature calculation unit that calculates an injector temperature based on a coil resistance value of an injector; an internal-combustion engine temperature calculation unit that calculates a temperature (L3, L4) of the internal combustion engine based on the injector temperature (Li); and an operating-state control unit that controls an operating state of the internal combustion engine based on the temperature (L3, L4) of the internal combustion engine calculated by the internal-combustion-engine temperature calculation unit, a cold/warmed-up state determination unit that determines whether the internal combustion engine is in a cold state or a warmed-up state; an ambient-temperature calculation unit that calculates an ambient temperature around the internal combustion engine control device; the internal combustion engine control device further comprises a correction unit that corrects the temperature of the internal combustion engine calculated based on the injector temperature by a subtraction amount, when it is determined that the internal combustion engine is in the cold state and a difference between the injector temperature and the ambient temperature is equal to or larger than a first predetermined value, and the correction unit calculates an initial value of the subtraction amount based on a relative relation with respect to the difference between the injector temperature and the ambient temperature, and decreases the subtraction amount with a passage of time since start-up of the internal combustion engine.