A transdermal administration device including an administering part including a substrate having a first surface, and at least one projection protruding from the first surface. The projection has a shape which extends along the first surface and includes one linear top edge which is located away from the first surface and has a first end and a second end, two primary lateral faces which share the one linear top edge and have lateral edges each individually connecting the first surface with the first end, and a secondary lateral face which has the lateral edges in common with the respective two primary lateral faces and forms one corner together with the two primary lateral faces. One of the lateral edge and the top edge on the primary lateral face form an obtuse angle, and the two lateral edges on the secondary lateral face form an acute angle.
