A projection for puncturing the skin includes a projection having a through hole that penetrates the projection along an extending direction of the projection, and a tubular member having a supporting surface as an end surface which is a flat surface for supporting the projection, and configured to be pressed against a skin to supply a fluid into the through hole of the projection. The projection has the length H along the extending direction of the projection, and the supporting surface has an area S, and the ratio of the area S to the length H (S/H) ranges between 2.1 and 10.5, inclusive.
