Abstract: Underwear according to the present disclosure may include an underwear portion and a band portion. The underwear portion may include a back side as an opposite side of a front side, in which the back side includes a cleft-fitting region that deforms to conform to the shape of an intergluteal cleft after underwear is worn. The band portion may include a cleft-fitting band disposed in a corresponding direction along the cleft-fitting region and a support portion supporting the cleft-fitting band. According to the present disclosure, underwear for women with a leak-proof function tightly fitting to a human intergluteal cleft can dramatically prevent the body fluids generated during menstruation from leaking through, by using the band portion including the cleft-fitting band disposed in a corresponding direction along the cleft-fitting region and the support portion supporting the cleft-fitting band.