An effective way to reduce the weight of vehicle body seems to be application of new materials, and such trend is remarkable. Among the various materials for automobile body, stainless steel sheets and cold rolled steel sheets are under the interests. However, in order to guarantee reliability of new material and to establish the long life fatigue design criteria for body structure, it is necessary to assess spot weldability and fatigue strength of spot welded lap joints fabricated under optimized spot welding condition. In this paper, spot weldability of stainless steel sheets, STS301L and STS304L, and cold rolled steel sheets, SPCC and SPCD. Fatigue strength of lap joints spot welded between similar and dissimilar materials were also assessed.