A fuel tank ventilation valve for a Laval nozzle, which has a sensitive regulation of the through flow quantity. The valve has a valve seat which is embodied on a valve seat body which has at least one opening that can be closed by the valve member. A cross section of the at least one opening is embodied as essentially smaller than an entry cross section of the Laval nozzle that is disposed spaced apart from the valve seat. The valve is suited for a metered introduction of fuel that has evaporated from a fuel tank of a mixture-compressing internal combustion engine with externally supplied ignition into an intake tube of the engine.