To provide a male screw which is easily screwed, has a high tightening torque after screwing, and is not easily loosened.SOLUTION: The male screw according to the present invention is a male screw having a shaft member and a screw thread formed in a spiral shape on the outer peripheral surface of the shaft member, and the lead of the leading side flank of the screw thread La and the lead of the flank on the following side of the thread is Lb, the leading flank and the trailing flank of the thread are formed so as to satisfy La
