Rolling bearing holder unit

A rolling bearing holder unit disclosed herein includes: a rolling bearing with a predetermined rotation axis, the rolling bearing including: an outer ring; an inner ring placed inward relative to an inner circumferential surface of the outer ring to be coaxial with the outer ring; and a plurality of rolling bodies placed between the outer ring and the inner ring; a bearing holder placed in contact with an outer circumferential surface of the outer ring or an inner circumferential surface of the inner ring in the rolling bearing; and a strain gauge with a resistor that is configured to detect a strain of the outer ring or the inner ring. In this rolling bearing holder unit: the bearing holder has a thick part and a thin part that is thinner than the thick part; the strain gauge is placed on the thin part; the rolling bearing is preloaded to form a predetermined contact angle; and the thick part is placed in contact at least with a region extending from an intersection of a straight line indicating the predetermined contact angle and the outer circumferential surface of the outer ring or the inner circumferential surface of the inner ring, to a preloaded end surface, the preloaded end surface being an end surface of the outer ring or the inner ring located nearer to the intersection.