Apparatus for measuring blood pressure is housed in a hermetically sealed, small casing, which is sealed in dust, water and pressure-tight manner by a film on the outside of the casing's cover and on the casing's underside. Pneumatic connecting lines are integrated into the casing cover and consequently separate the pressure-side area from the pressureless area in the casing interior. The casing interior contains a pump for filling a blood pressure cuff that is connectable to the apparatus, a valve for the controllable venting of the cuff, pneumatic connecting lines, pressure sensors and an electric control circuit and electric connecting lines. As a result of the construction according to the invention it is possible to obtain a high integration density and therefore a very small and compact blood pressure measuring module.