Disclosed is a ball bearing including an inner ring and an outer ring spaced apart from each other, each being rotatable, a cage part including a first cage and a second cage rotatably installed between the inner ring and the outer ring, and having ball receiving part formed along circumferential direction, ball installed in the ball receiving part, and rotating with the cage part as at least one of the inner ring and the outer ring rotates, and magnet which provides a magnetic force to the ball, wherein the first cage has a first seating part which is formed between the ball receiving parts, and on which one side of the magnet is placed, and the second cage has a second seating part which is connected to the first seating part, and on which the other side of the magnet is placed.