The IR laser welding of aluminum and copper materials for lithium-ion battery cells has limitation due to unsatisfactory joints strength caused by their low absorptivity and high re ectivity. To overcome these problems, this study has applied beam oscillation to increase the joint area of welded joints. A 1000 series aluminum alloy and oxygen-free copper sheets with a thickness of 0.5 mm were lap joints welded through 2.5 kW ber laser welding. The effect of the welding parameters of amplitudes (0, 0.2, 0.4, 0.6 mm) on weldability in welded joints has been investigated. The result con rmed that as the amplitude increases, the width at the interface increases, and penetration depth decreases. Furthermore, the maximum width at the interface could be obtained at approximately 1.23 mm under a travel speed of 100 mm/sec and amplitude of 0.6 mm. In addition, the tensile-shear load increased with higher amplitudes, and the maximum tensile-shear load was 1.1 kN in the amplitude of 0.6 mm with a travel speed of 400 mm/sec.