In a linear guide apparatus including a guide rail, a slider hanging over the guide rail to freely move with respect to the guide rail through the rolling movements of balls and a ball retainer mounted within the slider for holding the balls, the ball retainer is formed of plate-shaped metal and includes two ball holding parts respectively formed by bending the two side edge portions of a thin metal plate and two thin-plate shaped inner seal parts extending along and fixed integrally to the ball holding parts with the end portions thereof slidingly contactable with the upper surface of the guide rail. The ball retainer has not only a ball retainer function to be able to hold a large number of balls loaded into the ball rolling grooves formed in the slider but also an inner seal function to prevent foreign matter which have passed through side seals into the slider from entering into the ball rolling grooves.