To position a material surely as well as to make the number of working pieces reducible by making a shank surface harder than this metallic material, forming plural pieces of spiral ridge parts into being sharply pointed, and making an outer diameter of the thread ridge part larger than an inner diameter of a nail hole.

Plural pieces of ridge parts 21 have a triangular section each, and individual ridges are twisted as far as 0.5 to two times ranging from a base end to the tip of a shank 20. A surface of this shank 20 is harder than a soft steel metallic material, but it is softer than a shank surface of the conventional screw nail. In addition, an outer diameter D1 of the ridge part 21 is larger than an inner diameter (d) of a nail hole 31 of a metallic material 30, and an outer diameter D2 of a root part 22 is smaller than the inner diameter (d) of the nail hole 31. When a screw nail is driven into lumber through the nail hole 31, the ridge part 21 bites into a peripheral part of the nail hole 31, and thereby a V-shaped notch 32 is formed in the peripheral part, and the ridge part 21 is guided by this notch, therefore a nail gets into the lumber as rotating. With this constitution, since this screw nail is hard to be pulled out, the number of service pieces is reducible, and thus it is firmly fitted in the nail hole of the mettalic material, making any possible dislocation of the metallic material preventable from occurring.