Weigh-in-Motion measures vehicle load on roadway without stopping traffic. Bridge Weigh-in-Motion (BWIM) uses bridges as a weight scale. The advantages of BWIM are its invisibleness to drivers, low cost and simple installation. This study tested a potential of "Contactless Bridge Weigh-in-Motion" without any sensor in bridge. A digital high-speed camera captured bridge deflection by long distance lens, and another camera captures passing vehicle on road surface. Gross vehicle weight is calculated by influence area method by integration of deflection time history and estimated vehicle speed by traffic image. The accuracy of the BWIM system was under 20% for test vehicles with known gross vehicle weight.