Friction Stir Welding (FSW) is one of the modern and constantly evolving technologies of solid state joining and is used for welding a wide range of materials. The main parameters of friction stir welding such as rotational speed of the tool, movement speed and the angle of a tilt are analyzed in this article. 6XXX aluminium alloys have been investigated. The examined mechanical properties of the welds include hardness and strength, which are both important sources of information about quality of welding of the materials used in constructions.