To provide an artificial leak device capable of providing the relation between atmospheric pressure-converted leak quantity and change of detected pressure without determining a work capacity in an air leak tester and precisely and easily changing the leak quantity.

This artificial leak device is to be connected to the air passage of the air leak tester together with a pressure sensor. This device comprises a decompression part A for reducing the test pressure from the air passage and a flow detection part B connected between the decompression part A and the atmospheric side. The decompression part A comprises a body 10 having an artificial leak passage 12a, an elastically deformable pressure reducing element 11 formed of a porous foamed resin arranged in the artificial leak passage 12a, a pressing member 23 for pressing and compressing the pressure reducing element, and an adjusting mechanism 30. The adjusting mechanism 30 adjusts the position of the pressing member 23 to adjust the compression degree of the pressure reducing element 22, and also regulates the flow rate of the air passing in the flow detection part B.