The present invention relates to a demolding method and device, being used for detaching a mold and a substrate after completing an imprinting process, in which the mold is forced to detach from the substrate partially and form a gap therebetween by inserting at least a blade module between the two, and thus, as air is sucked into the gap and the adhesion force of vacuum effect exerting between the mold and the substrate is eliminated, the blade module is further applied to detach the mold from the substrate completely.