Leak detection device for measuring the differential pressure between a test chamber (10) and a reference chamber, which can be separated from the test chamber (10) gas-tight by a first check valve (24), wherein a differential pressure sensor (34) is connected to the reference chamber and to the test chamber (10) in order to measure the differential pressure between the internal pressure of the reference chamber and the internal pressure of the test chamber (10), characterized in that the test chamber (10) and the reference chamber each have at least one wall region formed from a flexible film, wherein the ratio of the test chamber volume (20) to the surface area of the flexible wall region of the test chamber (10) adjacent to the test chamber volume (20) and the ratio of the reference chamber volume to the surface area of the flexible wall region of the reference chamber adjacent to the reference chamber volume are substantially equal.