A linear motion guide unit is provided which is downsized in size, maintenance-free for lubrication, and makes it possible to assemble easily and quickly the slider with accuracy. The end cap has outward end surfaces each of which is concaved to provide a first recess to fit over a lubricant applicator of porous compact to apply the rollers while running through the turnaround passages, and a second recess to fit over a retainer plate. The retainer plate is surrounded with a peripheral edge of the end cap and held in place with a snap-fit engagement with the end cap to squeeze the lubricant applicator inside the first recess in the end cap.