A linear motion guide unit is disclosed in which the lubrication points of lubricant around a rolling element are made in a turnaround passage to ensure proper and steady lubrication by the lubrication system simple in construction, with accompanying sustainable maintenance-free condition for lubrication. A hole open to the turnaround passage is bored through an outward end surface of an end cap. A lubricant reservoir of porous compact product fits into a recess made in the outward end surface of the end cap. The lubricant reservoir has noses protruding to fit into the hole in the outward end surface of the end cap to expose itself to the turnaround passage in such a way forming a part of the curved wall of the associated turnaround passage. The noses come into rolling-touch with the rollers as they roll through the turnaround passage, applying the rollers with lubricant delivered from the noses.