A plurality of projections in a transdermal administration device each include a columnar portion extending from a first surface of a substrate, and a tapered portion extending from a top of the columnar portion. A maximum angle of an apex of the tapered portion viewed in a direction parallel with the first surface is in a range of 10° or more and 30° or less, a ratio of a length from a proximal end to a distal end of the tapered portion to a length from a proximal end to a distal end of the projection as viewed in a direction perpendicular to the first surface is in a range of 0.45 or more and 0.75 or less, and a pitch (distance between centers of closest projections), viewed in a direction perpendicular to the first surface is in a range of 50 μm or more and 350 μm or less.
