A linear motion guide unit is disclosed in which an end cap of a slider has a tube therein to feed even minor amounts of lubricant into a circulating circuit for rollers with no lubricant leakage, making sure of positive lubrication irrespective of working orientations or postures of the linear motion guide unit. A flexible tube made of fluorocarbon polymers is installed in the end cap to run from a lubricant inlet to a turnaround passage, thereby providing a lubricant-supply passage. A distal end of the tube fits into a three-way member made open to the turnaround passage on a spacer part, which is nested inside the end cap.