A woman's undergarment with cup sections, comprising: a pair of left and right brassiere cups each adapted to receive a breast and having a lower edge, a side edge, and an upper edge, the lower edge being downwardly curved, the side edge rising from an underarm-side end of the lower edge toward the upper edge, the upper edge extending from a sternum-side end of the lower edge to an upper end of the side edge; cup cover pieces each disposed to cover an outer surface of the brassiere cup and separated from the outer surface of the brassiere cup, wherein the lower edge of the brassiere cup extending from the underarm-side end to the sternum-side end is sewn to a lower edge of the cup cover piece, and the side edge and the upper edge of the brassiere cup are detached from the cup cover piece; a support panel to which the lower edges of the brassiere cups and the lower edges of the cup cover pieces are sewn together; back pieces extending from left and right sides of the support panel and adapted to cover a back of a wearer; straps each extending from the cup cover piece to the back piece; characterised in that it further includes lift-up pieces each disposed between the brassiere cup and the cup cover piece, having a lower edge that is sewn to the lower edge of the brassiere cup and an upper end edge that is connected to the strap, and thereby configured to lift the brassiere cup from below, wherein the brassiere cup has an opening in a corner region including the upper end, the lift-up piece includes an insertion portion having a strip shape extending toward the upper end edge, and the insertion portion is inserted through the opening in the corner region of the brassiere cup from the outer surface to an inner surface of the brassiere cup. a pair of left and right brassiere cups each adapted to receive a breast and having a lower edge, a side edge, and an upper edge, the lower edge being downwardly curved, the side edge rising from an underarm-side end of the lower edge toward the upper edge, the upper edge extending from a sternum-side end of the lower edge to an upper end of the side edge; cup cover pieces each disposed to cover an outer surface of the brassiere cup and separated from the outer surface of the brassiere cup, wherein the lower edge of the brassiere cup extending from the underarm-side end to the sternum-side end is sewn to a lower edge of the cup cover piece, and the side edge and the upper edge of the brassiere cup are detached from the cup cover piece; a support panel to which the lower edges of the brassiere cups and the lower edges of the cup cover pieces are sewn together; back pieces extending from left and right sides of the support panel and adapted to cover a back of a wearer; straps each extending from the cup cover piece to the back piece; characterised in that it further includes lift-up pieces each disposed between the brassiere cup and the cup cover piece, having a lower edge that is sewn to the lower edge of the brassiere cup and an upper end edge that is connected to the strap, and thereby configured to lift the brassiere cup from below, wherein the brassiere cup has an opening in a corner region including the upper end, the lift-up piece includes an insertion portion having a strip shape extending toward the upper end edge, and the insertion portion is inserted through the opening in the corner region of the brassiere cup from the outer surface to an inner surface of the brassiere cup.