To provide a rolling bearing device easily fastening two inner rings by a fastening ring.

This rolling bearing device 1 has an outer ring, the two inner rings 3, two or more rolling elements 4 arranged between the outer ring and the inner rings 3, and the fastening ring 5 fastening the two inner rings 3. The fastening ring 5 has an annular body part 5a and right and left engagement pieces 5b extending outward in a radial direction from both the axial ends of the body part 5a. The right and left engagement pieces 5b are pushed by the inner rings 3 relatively moved axially, elastically inclined axially, and elastically returned, thereby engaged with engagement grooves 3c1 formed into the inner peripheral surfaces of the inner rings 3.