A linear motion guide unit is disclosed which makes it possible to a long-lasting steady application of lubricant and also makes sure of preventing effectively occurrence of particles of dirt. The linear motion guide unit is comprised of a guide member, more than one rolling element, and a slider supported for linear movement along the guide track rail by virtue of rolling elements, the slider being made therein with a fore-and-aft hole in which a sleeve fits to allow the rolling elements to roll through there. The sleeve is made of a cellular member impregnated with lubricant in vacuum atmosphere.