The air flow inhaled into the internal combustion engine is calculated based on the operation state of the electric motor, the operational state of the bypass valve and the signal of the intake air flow sensor. Immediately after the bypass valve is opened when the electric motor is running, the air flow inhaled into the internal combustion engine may be calculated by acquiring the bypass air flow through the bypass passage and using the acquired bypass air flow to correct the intake air flow measured from the signal of the intake air flow sensor. Based on the calculated air flow inhaled into the internal combustion engine, control parameters which concern the output power of the internal combustion engine are adjusted.