Abstract: In order to investigate on effect of plate thickness on shear strength and fatigue strength of stainless steel laser lap welded joints,tensile tests and fatigue tests on stainless steel laser lap welded joints with two different plate thicknesses of 0. 8 mm + 2 mm and 2 mm + 2 mm were conducted. The results showed that shear strength and fatigue strength of the 2 mm + 2 mm joint were higher than those of 0. 8 mm + 2 mm. It was found by failure analysis that tensile fracture of the two joints was caused by shear fracture of weld, and fatigue cracks originated in heat-affected zone near the weld nugget on the inner surface of the incompletely welded plate. The crack propagated along the edge of the weld nugget to the outer surface of the incompletely welded plate until it penetrated the incompletely welded plate. It could be seen from the finite element force analysis of welded joints that the difference in the degree of stress concentration between the two joints was the main reason for the difference in their shear strength and fatigue strength.