To provide a full type ball bearing having a deep groove in which a scratch is hardly made at a ball and a bearing washer when the ball is assembled, the ball can be easily assembled and at the same time a separation of the bearing can be positively prevented and its assembly into a device can be easily carried out.

An inner ring 30 comprises: an inner ring member 40 having an inner ring raceway surface 48 and a ball setting groove 46 formed at an outer peripheral surface 30b, a step part 42 circumferentially arranged at an inner peripheral edge 30c and having a thin walled ball setting groove 46; and an inner ring annular member 50 engaged with the step part 42. An outer ring 31 comprises: an outer ring member 41 having an outer ring raceway surface 49 and a ball setting groove 47 formed at an inner peripheral surface 31a, a step part 43 circumferentially arranged at an outer peripheral edge 31c and having a thin walled ball setting groove 47; and an outer ring annular member 51 engaged with the step part 43. The inner ring member 40 and the inner ring annular member 50, and the outer ring member 41 and the outer ring annular member 51 are connected by a connecting means 70 in such a way that their relative motion in a diametral direction and a peripheral direction can be carried out and their relative motion in an axial direction cannot be carried out, respectively.