The screw comprises a circular rod, a tip, a tool connecting part, a thread part, and multiple protruding ribs. The circular rod has a centerline, a tail end, and a head end. The tip is formed on the tail end. The tool connecting part is formed on the head end. The thread part helically extends from an outer surface of the tip to an outer surface of the circular rod. The multiple protruding ribs are formed on an outer surface around the tail end and disposed in multiple thread pitches of the thread part from the tip. The multiple protruding ribs straightly extend on the circular rod and are parallel to the centerline, and provide a reaming effect to reduce resistance when the tip of the screw is screwed into the workpiece. So chips are smoothly discharged from the workpiece.