Abstract: A ball retainer chain includes a flat belt with axially arranged holes defined thereon. A separating portion is disposed between every two holes; upper/lower spacers combine with the separating portion. The surface between the separating portion and the adjacent hole is formed by a smooth surface. Partial spacer is formed by a spherical surface that smoothly connected to the hole surface. The spherical surfaces interlacedly arranged at a right side a left side include an opening with a vertical direction and a lateral directions corresponding to the flat belt, so that a mold pair reliant on a slantwise opening and closing manner would complete an injection molding. A smooth cylindrical form at two ends of the flat belt connects to an indentation at an inner or a mold surface of the flat belt. Thereby, while applying the belt to a linear guide apparatus, the cylindrical form could adjustably bend inward or outward for achieving a fluent traveling.