Abstract: A cuff for a blood pressure meter includes material that does not stretch and in which the length of the surface in contact with the finger does not vary when the cuff is filled with compressed air, regardless of the diameter of the finger. Because the internal pressure in the cuff closely approximates the blood pressure of the finger, the device is accurate. Compressed air is pumped into chambers formed by a basic structure and containment walls. Folded portions which are provided on the containment walls cause surfaces of the containment walls which contact the object to be measured to remain parallel to protruding bodies located on the basic structure as they are displaced by inflation of the chambers.