A round hole chamfering device for an automobile die comprises a drill bit, a drill shank and a shell. Two ends of the drill shank are connected with the drill bit and the shell respectively, a slide sleeve is arranged on the inner side of the shell, the drill shank is provided with a screw groove which is matched with the slide sleeve, and a spring is connected to the tail end of the screw groove. Due to avoidance of large cutting force, round hole chamfering of the automobile die can be performed anytime anywhere without adoption of excessive pneumatic tools for preparation is avoided, so that chamfering efficiency is greatly improved, and cost is reduced sharply.