Technology which enables a first member and a second member to be fastened together strongly is provided. A bar-shaped section is formed on the first member, a hole is formed in the second member, and the bar-shaped section of the first member is pressure fitted into the hole of the second member. Here, the diameter of the circumscribed circle which circumscribes the cross-section perpendicular to the axis of the bar-shaped section is made greater than the diameter of the inscribed circle which inscribes the cross-section perpendicular to the axle of the hole. The diameter of the inscribed circle which inscribes the cross-section perpendicular to the axis of the bar-shaped section is made smaller than the diameter of the circumscribed circle which circumscribes the cross-section perpendicular to the axle of the hole. A tapered section, in which the side face is inclined with respect to the axial direction, is formed in the side face of the harder of the bar-shaped section and the hole, in the end portion which is positioned to the forward side during pressure fitting.