A transdermal administration device including an administration member including a substrate having first and second surfaces, and a projection protruding from the first surface, a first adhesive sheet adhered to and extending outward from the second surface, a second adhesive sheet adhered to and extending outward from the first adhesive sheet, and a cover including a main body and a flange extending outward from an edge of the main body. The main body and the flange form a structure body including a remaining portion which includes at least a portion of the flange and is configured to remain on the second adhesive sheet, a tear-off portion which includes at least a portion of the main body and is configured to be separated from the remaining portion, and a tear-off assistance portion configured to facilitate formation of a cut for separating the tear-off portion from the remaining portion.