A method of manufacturing a thin film transistor substrate includes a first process in which a gate line pattern including a gate line and a gate electrode is formed with a first conductive material on a substrate using a first mask, a second process in which a first insulating layer is formed on the substrate and a data line pattern including a data line, a source electrode, and a drain electrode is formed with a second conductive material using a second mask, and a third process in which a second insulating layer is formed on the substrate and a pixel electrode connected to the drain electrode is formed on the second insulating layer with a third conductive material.