Stud joints of 2017 aluminum alloy were friction welded and its joint strength was examined. A stair zone formed at the weld interface. Although the hardness of the stair zone was almost the same as base metals, the heat affected zone of the bar and the plate was softened. The tensile strength of joints tended to increase with a pressure and a friction time, and the highest tensile strength was 275 MPa (63.1%joint efficiency for the bar base metal).In the bending testing, joints were cracked in the weld zone at bending angle of less than 5°. In the fatigue testing, joints fractured near the weld interface and the fatigue strength of joints increased as the tensile strength of joints was high.