A self-drilling screw is in particular to a drill portion having a non-threaded first drilling section connecting with the shank and a second drilling section connecting with said first drilling section and forms two grooves therein. Moreover, the whole first drilling section is formed as an oval-shaped pillar and it has two ridges extending therefrom. Furthermore, the diameter of the first drilling section is smaller than the diameter of the second drilling section, and the length of the second drilling section is between the length of one-third drill portion and the length of two-thirds drill portion. Therefore, due to the aforesaid features and the two drilling sections, the molds for manufacturing the screws suffer less damage while in operation and the manufacturing cost is therefore reduced. The present invention is also good at increasing the screwing speed. Moreover, the surface of the first drilling section also has the function of allowing the user to engrave a mark thereon.