This bearing device (1) for vehicle wheels comprises: an inner undercut part (8) provided in a portion at which an inner rolling surface (3d) formed on the inner side of an inner member (3) and an inner flange surface (3m) of the inner rolling surface (3d) intersect; an outer undercut part (9) provided in a portion at which an inner rolling surface (3c) formed on the outer side of the inner member (3) and an outer flange surface (3n) of the inner rolling surface (3c) intersect; and a vehicle wheel installation flange (3e) provided at a portion adjacent to the inner rolling surface (3c) formed on the outer side of the inner member (3), wherein, when the radius of curvature of the inner undercut part (8) is Ri, and the radius of curvature of the outer undercut part (9) is Ro, the relationship of Ri