At the time of stopping operation of the vehicle, the pressures inside of the fuel tank (5) and inside of the canister (6) detected at every constant time are stored in the storage device. A learned neural network using the pressures inside the fuel tank (5) and inside the canister (6) for each fixed time stored in the storage device and the atmospheric pressure as input parameters of the neural network and using a case where perforation occurs in the system causing fuel vapor to leak as a truth label is stored. At the time of stopping operation of the vehicle, a perforation abnormality causing fuel vapor to leak is detected from these input parameters by using the learned neural network.