Method and device for diagnosing abnormality in vehicle

A vehicle abnormality diagnosing device for diagnosing an abnormality in a vehicle, the vehicle abnormality diagnosing device comprising:

• an air flow meter that detects a first intake air amount, which is an intake air amount of an internal combustion engine installed in the vehicle;
• an evaporated fuel treatment system that is connected to an intake passage of the internal combustion engine at a position on a downstream side of the air flow meter, and that introduces a purge gas containing evaporated fuel from a fuel tank into the intake passage when a purge control valve is opened;
• a second intake air amount calculation unit that calculates a second intake air amount, which is a theoretical intake air amount of the internal combustion engine;
• and
• an abnormality determination unit that detects the first intake air amount in a state in which the purge control valve has been opened, and determines a presence or an absence of an abnormality in the evaporated fuel treatment system using the first intake air amount and the second intake air amount.