PURPOSE: To reduce the roller repairing cost by holding ceramics roller members whose vertical section is a V-shape with a couple of holders, to be detachably to a shaft member and putting an elastic member between the holders and roller members.

CONSTITUTION: A stopper 14 is formed on a shaft member 12, holders 24, 26 are installed in both sides of roller members 30; the holders 24, 26 and roller members 30 are fixed on the shaft member 12 detachably by use of a nut 20. At this time, an elastic member 34 such as a conical spring is arranged between the holders 24, 26 and the roller members 30 formed of ceramics such as silicon nitride. By such a structure, the wear resistance of the members 30 is remarkably improved to extend the service lift. The service lift of the members 30 is further extended because the elastic member 34 reduces thermal stresses acting on the members 30. The roller repairing cost is remarkably reduced because the members 30 are independently changed.