Self-aligning ball bearing with two structures of bore cylindrical or tapered and retainers made of steel sheet or synthetic resins. Characterized by outer ring raceway is spherical shape, have so can compensate concentricity and deflection built into the error of the self-aligning ball bearing, but it shall not exceed 3 degrees between inner ring and outer. Two raceway of inner ring and groove for spherical outer ring, equipped with cylindrical roller bearing. On the surface of the outer ring raceway curvature center and bearing center consistent, so with automatic self-aligning ball bearing the same tone heart function. In there was a deflection axis, a hood, can automatically adjust, not to increase the bearing burden.