To provide the wheel side fitting part construction of a strut in which inconvenience such as difficulty of fitting of a suspension arm or interference to the other member at steering is prevented from generating, and the space of the knuckle side connecting part of the outer cylinder of the strut is easily insured.

The outer diameter of a knuckle lock part 1a is formed into a conical form so as to become smaller as it goes downward of a strut outer cylinder 1, the inner diameter of the through hole 5b formed in the strut connecting part 5a of the knuckle 5 is formed into a conical form so as to become smaller as it goes downward, a conical collar 6 is interposed between the conical outer circumferential face of the knuckle lock part 1a and the conical inner circumferential face of the through hole 5d, a projecting part 6a upward projecting by fixed length from the upper end opening edge part of the through hole 5d of the strut connecting part 5a is extendingly provided along the outer circumferential face of the strut outer cylinder on the upper end part of the collar 6, and the collar 6 downward projecting from the through hole 5b is threadely engaged with a nut 9 and fastened.