PURPOSE: To easily and completely form a slip-off stopping structure by a method wherein a tapered jig is press-inserted into a cylindrical axis hole having almost uniform inside diameter on the principal part, and plastic deformation is formed on the inside circumference of the axis hole.

CONSTITUTION: A tapered jig 3, having the outside diameter d1 of tip part smaller than the inside diameter D1 of a shaft hole 2 and the outside diameter d2 of the middle part larger than the inside diameter D1 of the shaft hole 2, is inserted into the shaft hole 2 of a housing 1. This jig 3 is press-inserted into the shaft hole 2, the inner circumferential part, ranging from the entrance part of the shaft hole 2 to the center part, is, plastically deformed, and an engaging protrusion 4 is formed. At this time, the jig 3 may be subjected to rotation, heat and supersonic vibration and the like. When a shaft 6, on which a protruding string 5 is formed on the outer circumference for slip-off stopping, is press-inserted into the shaft hole 2 with a slip-off stopping structure, the protrusion 4 and the string 5 of an adjustment shaft 6 are engaged, the coming off from the fine hole of the adjustment shaft 6 is prevented, and the shaft 6 can be maintained in a rotatable manner.