An apparatus for monitoring the air pressure in a pneumatic tire carried by the rim of a vehicle wheel, comprising a sensing element which is arranged at the rim ring and which can be deformed and acted upon by the tire pressure, with a permanent magnet as the measurement value generator, in the region of rotary movement of which is disposed a measurement value sensor which is fixed to the vehicle in a stationary position and which is connected to an evaluation circuit. The apparatus is reliable in operation and uncomplicated in structure.