A bumper of a driving tool has a cylindrical overall shape and also has a space portion expanding downward therein. The bumper is provided with an upper portion, an intermediate portion, and a lower portion. A normal inclined-surface, in which an outer diameter becomes larger from an upper end of a full height of the bumper toward a slightly upper position of the intermediate portion, is formed at a periphery of the upper portion. A bulging-out portion haying the largest outer diameter in the bumper is bulged out, at a periphery of the intermediate portion. A reverse inclined-surface, in which the outer diameter becomes smaller toward downward, is formed at the periphery of the lower portion.