A screw includes a shaft, a trumpet-shaped head provided to a base end of the shaft, and a narrow-tip portion formed at a tip end of the shaft. The shaft has different diameters at a small-diameter portion contiguous to the narrow-tip portion and at a large-diameter portion contiguous to the head. Two screw threads are formed on the small-diameter portion and one screw thread is formed on the large-diameter portion. Therefore, a thread portion can be divided into a double-thread portion and a single-thread portion. It is preferable that the screw threads forming the double-thread portion have different heights. The screw is mainly used for fastening a plasterboard to a frame member.