In a rolling bearing structured such that a plurality of rolling elements are respectively held between inner and outer rings by a retainer, grease is sealed in by a seal, a rotary body with the outer ring fitted therewith and a shaft with the inner ring fitted therewith can be connected together by a clutch mechanism and, when the rotary body and shaft are connected together by the clutch mechanism, the rolling bearing can be used on receiving a rotation load while the relative rotation between the inner and outer rings is zero, an initial radial clearance between the inner and outer rings is set such that a bearing effective clearance when the present rolling bearing is incorporated into between the rotary body and shaft can provide a positive value.