A woman's undergarment with cup sections includes a pair of left and right brassiere cups, cup cover pieces, straps, back pieces, a support panel, and lift-up pieces. A lower edge of each of the brassiere cups is sewn to a lower edge of the lift-up piece. A side edge and an upper edge of the brassiere cup are detached from the cup cover piece. The lift-up piece is disposed between the brassiere cup and the cup cover piece. The brassiere cup has an opening in a corner region including an upper end of the brassiere cup. An insertion portion of the lift-up piece is disposed to pass through the opening.