an apparatus for measuring gas leakage including a hollow container having a gas inlet port which is connected to a reference pressure gas supply via a valve and another gas outlet port that is connected to a test container ; a liquid container located in the hollow container , a balance mechanism mounted within the hollow container which is maintained in equilibrium by an inverted floating cup that is attached to the underside of the balance beam and which is immersed in a liquid contained in the liquid container , a supply pipe that introduces gas at a reference pressure into the floating cup , a detector which detects the inclination of the balance mechanism and generates a signal corresponding thereto , a measuring device that measures the displacement of the floating cup as a function of the signal from the detector , and a restoring means that will restore the equilibrium of the tilted balance beam .