Ball bearing

A ball bearing comprising:

• an inner ring having an inner ring raceway surface in an outer circumference;
• an outer ring having an outer ring raceway surface in an inner circumference;
• a plurality of balls rollably disposed between the inner ring raceway surface and the outer ring raceway surface;
• and
• a cage in which a plurality of pockets rollably holding the balls and having cylindrical surfaces are formed at intervals in a circumferential direction and which has a circumferential surface guided by an inner diameter surface of the outer ring or an outer diameter surface of the inner ring,
• wherein regarding each of the pockets, an inclination angle β of a corresponding one of the cylindrical surfaces is set more than 0° and less than a contact angle α of the ball bearing, and the cylindrical surface and a corresponding ball are in contact with each other at an inner side in a cage thickness direction relative to a position where a rotation axis of the ball intersects with the cylindrical surface at an intersection position, so that a space is formed at a portion from a contact position to the circumferential surface of the cage on a side closer to the intersection position,
• wherein the inner diameter surface of the outer ring or the outer diameter surface of the inner ring that guides the cage has the same diameter on both sides in an axial direction across the outer ring raceway surface or the inner ring raceway surface, and
• wherein an outer circumferential surface of the cage guided by the inner diameter surface of the outer ring or an inner circumferential surface of the cage guided by the outer diameter surface of the inner ring has the same diameter on one side in the axial direction and an other side in the axial direction.