PROBLEM TO BE SOLVED: To enable a high degree of blood pressure measurement accuracy even when the cuff is made narrower.SOLUTION: Provided is a bag-shaped structure 32 for use in a sphygmomanometer cuff 12, which cuff is wrapped around a living body and applies pressure to the living body with expansion as a fluid is supplied to an interior space thereof, the bag-shaped structure comprising: an inner wall section 41 provided on the living body side and having a Shore A hardness in the range of 15-75； an outer wall section 42 facing the inner wall section 41； and a pair of side wall sections 43 provided to be contiguous with the inner wall section 41 and the outer wall section 42, having a thickness identical to the thickness of the inner wall section 41, and having a Shore A hardness in the range of 20-95 which is larger than the Shore A hardness of the inner wall section 41.SELECTED DRAWING: Figure 2【課題】カフを狭幅化した場合であっても、高い血圧計測精度を達成可能とする。【解決手段】生体に巻き付けられ、内部空間に流体が供給されることで膨張し、前記生体を圧迫する血圧計用のカフ１２に用いられる袋状構造体３２であって、生体側に設けられ、Ｓｈｏｒｅ Ａ硬度が１５乃至７５の範囲内にある内壁部４１と、前記内壁部４１に対向した外壁部４２と、前記内壁部４１及び前記外壁部４２と連続して設けられ、前記内壁部４１の厚さと等しい厚さを有し、Ｓｈｏｒｅ Ａ硬度が２０乃至９５の範囲内にあり且つ前記内壁部４１のＳｈｏｒｅ Ａ硬度よりも大きい一対の側壁部４３とを備えた袋状構造体が提供される。【選択図】図２
