An adjustable lubrication module of a linear guideway includes an end lid disposed at a slider and an oil scraper disposed at the end lid. The end lid has therein two opposing backflow-chambers. A feed-hole disposed between the backflow-chambers and an oil-guiding conduit disposed below the feed-hole are disposed on the end lid. Communication between the feed-hole and the oil-guiding conduit is achieved by a primary oiling-channel. Communications between the oil-guiding conduit and the backflow-chambers are achieved by a secondary oiling-channel. Therefore, oiling-channel adjustment performed on the adjustable lubrication module operating in conjunction with the linear guideway does not entail demounting the end lid from the slider, thereby preventing ball missing. The feed-hole and the oil-guiding conduit are not disposed at the junction of the end lid and the slider; hence, lubrication oil is prevented from flowing over the gap between the end lid and the slider.