A supporter includes a small number of members and has a simple fitting method. It can give an intraperitoneal pressure rise effect to a supporter wearer, attain retroflexion suppression, and stabilize the sacroiliac joint. The supporter includes a base material which is formed of a knitted fabric by warp knitting and in which a knitting direction of the knitted fabric is set to be a longitudinal direction. Stretchability in the longitudinal direction is given, while stretchability in a short direction is suppressed. It has a back-supporting section that is a central portion of the base material, projection sections provided by projecting upward both end portions disposed on both sides of the back-supporting section, and curved sections each making the vicinity of the boundary between the back-supporting section and each of the projection sections. Each curved section is curved into a shape of approximate “”.