The present disclosure relates to a detecting device and a detecting method of a transparent display panel. The method comprises: providing a reference pattern sheet having n pairs of first regions with a first color and second regions with a second color alternately arranged in a first direction, and each of the first regions and each of the second regions having a same predetermined width D in the first direction; forming a uniform predetermined illuminance on the reference pattern sheet; detecting directly the reference pattern sheet by a measuring device; detecting the reference pattern sheet through the transparent panel display by the measuring device; and thereby determining a clarity of the transparent display panel.