To provide a rotary bearing device enabling the efficient removal and collection of leaking grease by setting grease leak points when grease is supplemented or the bearing is used at specified points in the circumferential direction.

This rotary bearing device 10 comprises an inner race 11 and an outer race 12 disposed on the inner side and the outer side of rolling elements 13, respectively and a seal member 15 for sealing between these races 11, 12 over the entire circumference. The rotary bearing device is disposed between an upper structure and a lower structure 1 supporting the upper structure. A seal force weakening part 30 is formed at the circumferential specified portion 15a by making the seal force of the circumferential specified portion 15a of the seal member 15 weaker than the seal force of the other portion 15b.