To provide a bearing device having simple construction preventing an unnecessary slip at starting rotation, suppressing a rise of a preload during high-speed rotation, and securing high spindle rigidity.

A spindle 3 of a machine tool is installed on a housing 2 via a load-side bearing 5A and a counter-load-side bearing 5B as angular ball bearings arranged back to back. The load-side bearing 5A has an outer ring 11A which is positioned and fixed onto the housing 2 in the axial direction, and the counter-load-side bearing 5B has an outer ring 11B which is not positioned and fixed to the housing 2 in the axial direction. The axial positions of inner rings 12A, 12B of both bearings 5A, 5B are restricted. The size of an axial internal clearance of the bearing 5B is positive in a room-temperature operation stopped condition and negative in an operated condition resulting from a temperature difference between the inner and outer rings and the operation of centrifugal force to produce the fixed-position preload. Between the back face of the outer ring 11B of the bearing 5B and the housing 2, an elastic body 10 is laid for energizing the outer ring 11B of the bearing 5B to the front-face side.