In order to apply aluminum alloys to structural components, they should be joined with sufficient strength and quality as high welding speed as possible. High-power laser welding is expected to achieve much higher productivity than conventional joining techniques. Welding of aluminum alloys was performed using 2-kW and 3-kW continuous wave Nd:YAG lasers. Two beams were delivered by optical cables 0.6 mm in diameter and focused on the surface of the specimens as dual spots. Overlap joints of 2-mm-thick sheets were made at various welding parameters, including beam distance, beam arrangement and welding speed. The quality of the bead, including its appearance and macrostructure, and the tensile strength of the joints were investigated. At a shorter beam distance of 0.36 mm, the weld bead surface was humped, making it unacceptable in terms of quality. Sound weld beads were obtained at beam distances of 0.6 mm and 1.0 mm. As the beam distance was increased, the weld depth became shallower. At a beam distance of 1.0 mm, the weld area was too small to provide sufficient strength.