Provided is a supporter with which an intraperitoneal pressure increasing effect can be given to a wearer of the supporter to achieve prevention of retroflexion and which can stabilize a sacroiliac joint. A supporter 100 includes a body section 10 having a back-contact section 11, loops 21 arranged on front surfaces of both ends of the body section 10, a first auxiliary band section 31 of which one end 31a is fixed to the top end of a left side 11c of the back-contact section 11 and the other end 31b is fixed to the bottom end of a right side 11d of the back-contact section 11, a second auxiliary band section 32 forming a pair with the first auxiliary band section 31, a first ring 41 arranged to slide between the one end 31a and the other end 32b of the first auxiliary band section 31, a second ring 42 forming a pair with the first ring 41, a first adjustment band section 51 of which one end 51a is fixed to the loops 21 on a right end 10b side of the body section 10 and the other end 51b can be fastened to the loops 21 on the right end 10b side of the body section 10, and a second adjustment band section 52 forming a pair with the first adjustment band section 51.