This paper investigates the tensile properties of the friction stir welded joints of Al 7075-T651 aluminum plate according to the welding conditions. A 7075-T651 aluminum alloy plate with a thickness of 6.0 mm was used in this investigation. For the friction stir welding (FSW) process, a tool with shoulder diameter of 20 mm and probe diameter of 9 mm was used. The rotation speed and traverse speed conditions were changed in this study, the other welding conditions are constant. The welding direction was aligned with the material rolling direction, and dimension of the FSW plate were $250{ imes}100{ imes}6;mm$. As far as this work is concerned, the optimal FSW conditions are determined as the rotation speed, 600 rpm and traverse speed 0.8 mm/sec or the rotation speed, 800 rpm and traverse speed 0.5 mm/sec.