This paper deals with the strengthening of spot welded lap joints by increasing the opening angle on the nugget edge. Based on the equation proposed by past researchers to predict the strength, the factor necessary for the strengthening was extracted. And, based on this factor, the strengthening of spot welded lap joints was examined. First of all, in order to increase the opening angle on the nugget edge, the vicinity of the nugget edge was bended with a bending machine. Next, cross tension strength tests were conducted into the spot welded lap joints with various opening angles on the nugget edge. Finally, the relationship between cross tension strength and the opening angles on the nugget edge was clarified. As a result, by increasing the opening angles on the nugget edge, we found that the cross tension strength could be improved by 20%.