The purpose of this research is to investigate the effect of the main factor of the surface roughness in aluminum alloy (Al-2024) as a workpiece and face milling machining by using computer numerical controlled milling machine with 50 millimeter diameters of the tool with triple cutting edges of carbides. The controlled factors were the speed, feed rate and the depth of cut and this factors effect on the surface roughness. The result of the tests showed that the surface roughness was likely to reduce when the cutting speed increase. It is found the surface roughness is increase with increasing both of feed rate and depth of cut. then drawing a charts illustrate the relationship between variables (cutting speed, feed rate and depth of cut) with surface roughness and analysis resulting data by utilizing the SPSS software to predicted surface roughness by using milling machining parameters and graphical analysis of the obtained data, The percentage of accuracy was 96%.