An active device array substrate and a fabricating method thereof are provided. A first patterned conductive layer including separated scan line patterns is formed on a substrate. Each scan line pattern includes a first and second scan lines adjacent to each other. Both the first and the second scan lines have first and second contacts. An open inspection on the scan line patterns is performed. Channel layers are formed on the substrate. A second patterned conductive layer including data lines interlaced with the first and second scan lines, sources and drains located above the channel layers, and connectors is formed on the substrate. The sources electrically connect the data lines correspondingly. At least one of the connectors electrically connects the first and second scan lines, so as to form a loop in each scan line pattern. Pixel electrodes electrically connected to the drains are formed.