High blood pressure measurement accuracy is made possible even with a cuff reduced in width. Provided is a bag-shaped structure for use in a cuff for a blood pressure monitor that is wrapped around a living body and is inflated by supplying a fluid to an internal space to apply a pressure to the living body, including an inner wall portion that is provided on a living body's side and has a Shore A hardness within a range of 15 to 75, an outer wall portion that faces the inner wall portion, and a pair of side wall portions that are provided in a manner to be continuous with the inner wall portion and the outer wall portion, have a thickness equal to a thickness of the inner wall portion, and have a Shore A hardness that falls within a range of 20 to 95 and is larger than a Shore A hardness of the inner wall portion.
