A method for forming a metal line of a semiconductor device forms an aluminum line having an excellent orientation. A specific resistance of a metal line is reduced, thereby enabling sufficient supply of a desired electric current. The method includes steps of forming a lower reflection preventing layer on a silicon wafer, forming a first aluminum layer on the lower reflection preventing layer, forming a second aluminum layer on the first aluminum layer, lowering a surface roughness of the second aluminum layer, forming an upper reflection preventing layer on the second aluminum layer, and forming an aluminum line.