A Bi base material of which a Miller index (202) face has the index of orientation of not less than 30% and in which the (202) face has the index of orientation assuming a maximum value as compared with those of other faces forms a minute structure and has a surface which is not a mirror finished surface but a fine, irregular surface on which minute and uniform projections in the form of a triangular pyramid or a quadrangular pyramid congregate. Therefore, the surface easily retains oil thereon to be improved thereby in oil wettability, as a result of which an improvement in anti-seizure is achieved.