To prevent the occurrence of a slide during the use of a pipe and a clamp fitment and secure safety and reduce weight by a method where the strength (hardness) of at least a body of a steel pipe, hardness of which is increased, and a clamp fitment is made equal to each other.

In a clamp fitment 10 where body 1 made of a steel and a cover 2 are pivotally secured and a steel pipe 9 for being fastened is fastened by the body 1, the cover 2, a bolt 4, and a nut 6, the strength of the body 1 is adjusted to a level approximately equal to the strength of the pipe 9.