A first fluid bag and a second fluid bag are located side by side along an inner circumference of a belt, expand and contract upon entry and exit of a fluid, and are provided to press a measurement site from therearound while surrounding the measurement site. The fluid supply unit supplies the fluid to the first fluid bag and the second fluid bag. The pulse wave detection unit is disposed on an external surface portion of the first fluid bag and is provided to press the measurement site upon expansion of the first fluid bag. A position of the pulse wave detection unit relative to the artery passing through the measurement site is adjusted through adjustment of a ratio between a volume of the fluid in the first fluid bag and a volume of the fluid in the second fluid bag by the fluid supply unit.
