A ball retainer comprising: a chain belt having a first end and a second end opposite to the first end, and wherein a plurality of accommodating portions is between the first end and the second end; a hook arranged on the first end of the chain belt, wherein the hook comprises a neck portion, a hook body, two leaning protrusions, and a limiting protrusion; the neck portion extends outward from the first end along a long side direction of the chain belt; the hook body is connected to the neck portion, and a width of the hook body along a short side direction of the chain belt gradually decreases from a side of the neck portion to a direction away from the neck portion; the two leaning protrusions are arranged at a joint portion between the hook body and the neck portion, and the two leaning protrusions extend outward along the short side direction of the chain belt toward two sides of the hook body, respectively; the limiting protrusion extends outward from an end surface of the hook body away from the first end of the chain belt along the long side direction of the chain belt; and a slot portion corresponding to the hook and arranged on the second end of the chain belt, wherein the slot portion comprises a slot, two abutting portions, a connecting portion, and a receiving portion, wherein the slot has an opening side and a limiting side opposite to the opening side; the two abutting portions and the connecting portion are on the opening side, the two abutting portions extend inward from the slot along the short side direction of the chain belt, the connecting portion is connected to the two abutting portions, and the receiving portion is on the limiting side; wherein after the hook is correspondingly engaged with the slot portion, the hook body is accommodated in the slot, the two leaning protrusions correspondingly lean against surfaces of the two abutting portions facing the limiting side, the neck portion leans against the connecting portion, and the limiting protrusion is correspondingly accommodated in the receiving portion; wherein, after the hook is correspondingly engaged with the slot portion, an outer peripheral side and an inner peripheral side corresponding to the outer peripheral side are formed, and the limiting protrusion and the receiving portion are on the inner peripheral side. a chain belt having a first end and a second end opposite to the first end, and wherein a plurality of accommodating portions is between the first end and the second end; a hook arranged on the first end of the chain belt, wherein the hook comprises a neck portion, a hook body, two leaning protrusions, and a limiting protrusion; the neck portion extends outward from the first end along a long side direction of the chain belt; the hook body is connected to the neck portion, and a width of the hook body along a short side direction of the chain belt gradually decreases from a side of the neck portion to a direction away from the neck portion; the two leaning protrusions are arranged at a joint portion between the hook body and the neck portion, and the two leaning protrusions extend outward along the short side direction of the chain belt toward two sides of the hook body, respectively; the limiting protrusion extends outward from an end surface of the hook body away from the first end of the chain belt along the long side direction of the chain belt; and a slot portion corresponding to the hook and arranged on the second end of the chain belt, wherein the slot portion comprises a slot, two abutting portions, a connecting portion, and a receiving portion, wherein the slot has an opening side and a limiting side opposite to the opening side; the two abutting portions and the connecting portion are on the opening side, the two abutting portions extend inward from the slot along the short side direction of the chain belt, the connecting portion is connected to the two abutting portions, and the receiving portion is on the limiting side; wherein after the hook is correspondingly engaged with the slot portion, the hook body is accommodated in the slot, the two leaning protrusions correspondingly lean against surfaces of the two abutting portions facing the limiting side, the neck portion leans against the connecting portion, and the limiting protrusion is correspondingly accommodated in the receiving portion; wherein, after the hook is correspondingly engaged with the slot portion, an outer peripheral side and an inner peripheral side corresponding to the outer peripheral side are formed, and the limiting protrusion and the receiving portion are on the inner peripheral side.