To obtain a fixing element which is simple in constitution and may be well driven into a hard housing member by specifying the hardness of the adjacent and fixing regions of the fixing element which composes the fixing region and the adjacent region which is integral therewith and has a large diameter of steel.

The fixing element, such as bolt or nail, is composed of the fixing region 1 of the diameter DB and the adjacent region 2 of the diameter DA larger than the diameter DB of steel. The fixing region 1 has a cylindrical shaft 3 provided with a taper converging toward a pointed end 4 in the driving direction. The hardness of the adjacent region 2 of such fixing element is specified to 35 to 43HRC and the hardness of the fixing region 1 to 46 to 55HRC. The fixing region 1 is driven into the housing material in the driving work of such fixing element. As a result, high load is generated but the fixing region 1 has high rigidity and is, therefore, not deformed. The adjacent region 2 acts to fix an object to the housing member and has high toughness and, therefore, this region is capable of absorbing the dynamic tension elastically and casually generated in the fixing element without the failure of the element.