Ceramic and metal shafts are joined at their ends by brazing, with a buffer member being interposed therebetween. The joined ends of the ceramic and metal shafts and the buffer member are received within a metal sleeve and joined by brazing to part of the inner circumferential wall of the metal sleeve in such a manner than an axial end of the joint where the inner circumferential wall is securely joined to the ceramic and metal shafts is positioned between opposite axial ends of the metal sleeve and at the same time between opposite axial ends of the ceramic shaft. The outer circumferential wall of the metal sleeve is formed with an annular groove in the place corresponding to the above mentioned axial end of the joint with respect to the axial direction of the metal sleeve.