Roller bush for fuel injection pump

A roller bush for a fuel injection pump having a cam reciprocating a plunger, a metal roller forced to contact with the cam, and a pin supporting the roller rotatably about a rotational axis, the bush being interposed between the roller and the pin, the pin being supported at the either axial sides of the bush, wherein the axial end portions of the bush consist entirely of ceramic, each portion having an axial length from the corresponding axial end surface of L, and wherein a ratio of the axial length L to the entire axial length L0 of the bush is set to be equal to or larger than {(11-d)/16}, where d represents the inner diameter of the bush.