PURPOSE: To detect the leakage of a liquid mixing in an air flow easily without suffering from the effect of the speed of air stream by providing a capillary layer between the adjoining electrodes and by measuring the electrostatic capacity of between both electrodes.

CONSTITUTION: The detecting device 1 for liquid leakage is fitted to a wall face 8A and is consisted of a supporting body 2 having electric insulation fitted to the wall face 8A, electrode plates 3, 4 buried so as to oppose mutually into the supporting body 2 thereof and of a capillary tube, for instance, fiber layer 5 provided between both electrodes 3, 4 thereof. And in this invention, an oil 9A is invaded into the fiber layer 5 thereof and the electrostatic capacity of between both electrode plates 3, 4 is changed, so the electrostatic capacity is measured by an electrostatic capacity meter which is connected to respective terminals 6, 7 of the electrodes 3, 4 thereof. The leakage of the oil invaded into said fiber layer 5 can be detected easily without suffering from the effect of the air stream speed.