A side-locking ball bearing sliding rail assembly formed of a fixed rail, a movable rail, an auto-closing mechanism carrier plate, a sliding device, a linking member and a spring member is disclosed. The auto-closing mechanism carrier plate has a spring force adjustment member longitudinally adjustably mounted thereon and connected with an opposite end of the spring member for adjusting the restoring force of the at least one spring member. By means of adjusting the position of a spring force adjustment member on the auto-closing mechanism carrier plate, the restoring force of the spring member is relatively adjusted to fit different requirements, and thus, the side-locking ball bearing sliding rail assembly can be used for carrying different loads or to fit different size tolerances without making any modifications, or changing the drawer or the spring member, assuring a high level of operating smoothness and accuracy.
