A drill bit structure of a self-tapping screw is rotated clockwise to screw with a workpiece or is rotated counterclockwise to remove from the workpiece, and the self-tapping screw contains: a head, a shank, and a drill bit. The head is configured to connect with a tool. The shank integrally extends from the head. A conical face has a tip, two arcuate grooves, and two first cutting edges. Each of the first cutting edges is formed on a connection portion of each arcuate groove and the conical face. The drill bit includes two third cutting edges, and each third cutting edge is adjacent to the tip, shapes of the two first cutting edges correspond to shapes of the two third cutting edges respectively, and heights of the two first cutting edges are not less than the conical face. Each first cutting edge has a reinforcement portion.