PURPOSE: To simplify mounting and demounting a bearing by installing a member pressing a bearing outer ring inward, in an inner edge at the opening side of a bearing housing.

CONSTITUTION: A bearing 11 is composed of an outer ring 11a, an inner ring 11b and a ball 11c, and the outer ring 11a is held on a sectional V-shaped bearing housing 12, thereby assembling the bearing 11. Two pressing members 15 are formed in an opening inner edge of this housing 12, and the assembled outer ring 11a is constituted so as to be pressed inward. These pressing members 15, 15 are composed of a cylindrical body 15a being screwed in the bearing housing 12, a ball 16 being installed in the cylindrical body 15a and coming into contact with the outer ring 11a and a spring 17 energizing this ball 16 to the outer ring 11a side and simultaneously preventing the cylindrical body 15a from slipping off through a slipoff preventing bolt 18.