An electro-optical device substrate has substrate devices, each composed of at least a portion of an electro-optical device having an image display region, on a surface thereof, and is divided into the substrate devices along boundaries between regions where the substrate devices are formed. The electro-optical device substrate includes testing wiring lines which are provided in regions other than the substrate device forming regions on the substrate, and which are respectively supplied with testing signals for the substrate devices, two or more image signal terminals being electrically connected to each testing wiring line.