The structure of the contact points of the ignition switch is improper, and therefore, if the switch is operated extremely frequently, abrasion powder generated when the switch is operated may accumulate, which could cause the electricity to continue to flow. If this occurs, the starter motor may continue to rotate, in which case, the contact points may heat up, and subsequently foreign odour and smoke may come out from the abrasion power, leading to a fire in the worst case.