A woman's undergarment (A) comprising: a pair of left and right brassiere cups each configured to receive a breast (B) 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 (P1) of the lower edge toward the upper edge , the upper edge extending from a sternum-side end (P2) of the lower edge to an upper end (P3) 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 ; a back piece extending from lateral sides of the cup cover pieces and configured to cover a wearer's back; and straps each extending from the cup cover piece to the back piece , wherein: only the lower edge of the brassiere cup extending from the underarm-side end (P1) to the sternum-side end (P2) is sewn to a lower edge of the cup cover piece , and the side edge and the upper edge of the brassiere cup are free edges detached from the cup cover piece , characterized in that : the woman's undergarment (A) further comprises a cup connecting piece for connecting abutting portions of the left and right brassiere cups , each of the cup cover pieces includes: a cover piece body that covers the outer surface of the brassiere cup ; and an upper edge reinforcing strip sewn to an upper edge of the cover piece body , and a lower end portion of one of the upper edge reinforcing strips and a lower end portion of another of the upper edge reinforcing strips overlap each other to form a double-layer region, and the overlapping lower end portions are sewn together to a lower edge of the cup connecting piece . a pair of left and right brassiere cups each configured to receive a breast (B) 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 (P1) of the lower edge toward the upper edge , the upper edge extending from a sternum-side end (P2) of the lower edge to an upper end (P3) 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 ; a back piece extending from lateral sides of the cup cover pieces and configured to cover a wearer's back; and straps each extending from the cup cover piece to the back piece , wherein: only the lower edge of the brassiere cup extending from the underarm-side end (P1) to the sternum-side end (P2) is sewn to a lower edge of the cup cover piece , and the side edge and the upper edge of the brassiere cup are free edges detached from the cup cover piece , characterized in that : the woman's undergarment (A) further comprises a cup connecting piece for connecting abutting portions of the left and right brassiere cups , each of the cup cover pieces includes: a cover piece body that covers the outer surface of the brassiere cup ; and an upper edge reinforcing strip sewn to an upper edge of the cover piece body , and a lower end portion of one of the upper edge reinforcing strips and a lower end portion of another of the upper edge reinforcing strips overlap each other to form a double-layer region, and the overlapping lower end portions are sewn together to a lower edge of the cup connecting piece . the woman's undergarment (A) further comprises a cup connecting piece for connecting abutting portions of the left and right brassiere cups , each of the cup cover pieces includes: a cover piece body that covers the outer surface of the brassiere cup ; and an upper edge reinforcing strip sewn to an upper edge of the cover piece body , and a lower end portion of one of the upper edge reinforcing strips and a lower end portion of another of the upper edge reinforcing strips overlap each other to form a double-layer region, and the overlapping lower end portions are sewn together to a lower edge of the cup connecting piece . <EOS>