Abstract: Among plural liquid leakage sensors placed at the lower most portion of a system such as a floor surface, a leaked liquid storing portion, etc., an error-activated location of the sensor can be easily identified uniquely when the sensor is detecting any abnormality. In a liquid leakage detecting system including at least one liquid leakage sensor having at least one detecting portion contactable with a leaking liquid through an air layer or a liquid permeable layer, a warning device including a sound producing is placed within a specified spatial distance from each installation position of the liquid leakage sensor, wherein after detecting any abnormal conditions of the liquid leakage sensor, a warning signal is issued at least in an audio frequency based on the warning device in order to discriminate the error-activated leakage sensor from other non-activated leakage sensors placed outside of the specified spatial distance and uniquely identify the installation position of the activated leakage sensor.