In the case where predetermined abnormality detection performed with operation of an engine, such as abnormality detection of a fuel system and an ignition system of the engine and various sensors, has not been completed (in the case where an abnormality detection completion flag F is zero), self-sustaining operation of the engine is performed to continue the operation (S280) when the engine is being operated and a power demand Pe* of the engine is less than a threshold Pstop1 for stopping the operation of the engine in normal time (S130) but is a threshold Pstop2 or more smaller than the threshold Pstop1 (S200 and S210), and the engine is started when the engine is not being operated and the power demand Pe* is a threshold Pstart2 or more smaller than a threshold Pstart1 for starting the engine in normal time (S310 and S320). This ensures performance of the predetermined abnormality detection.