<p>[Problem] To provide a fitting structure which is configured so that the easiness of mounting of a shaft body fitting part to a main shaft body is sufficiently improved. [Solution] This fitting structure is configured in such a manner that a front end sloped surface is formed at the front end of a main shaft body so as to obliquely intersect the axis of the main shaft body. This eliminates the need for aligning a fitting hole and the main shaft body with each other before starting fitting work and the front most end of the main shaft body can be easily passed through the fitting hole by only roughly matching the positions of the front most end of the main shaft body and the fitting hole. Once the front most end of the main shaft body has been inserted into the fitting hole the edge of the front end sloped surface of the main shaft body does not butt against the edge of the fitting hole in the process of subsequent fitting work. As a result of this configuration the work is not hindered and the easiness of mounting of the shaft body fitting part to the main shaft body is sufficiently improved.</p>
