This failure determining device is provided with a first determining unit which refers to correction amount data indicating a correction amount relating to operation of a part related to an internal combustion engine, to determine whether there is a possibility that the internal combustion engine has failed, a data acquiring unit which, if it has been determined that there is a possibility that the internal combustion engine has failed, acquires influencing factor data indicating a factor influencing the correction amount, and a second determining unit which refers to the correction amount data together with the acquired influencing factor data to determine whether the internal combustion engine has failed.