To provide a rolling bearing that suppresses oscillation of a contact lip and can prevent the contact lip from being damaged even when the rolling bearing is used for inner wheel rotation and high speed rotation.

At a neck part 48 at an inner peripheral part of an air-tight device 40, a circular rib part 50 in a projected shape toward the inner side of an axial direction is formed. When the thickness of the neck part is T, the height of the rib part is L, and the thickness of the rib part is X, the rolling bearing 10 satisfies the inequalities of 1.5T≤L≤2.0T and 1.7T≤X≤2.0T.