Abstract: Urine detecting and signalling device for use in a diaper includes two pieces of flat conductive foil and a control unit. The two pieces of the foil are positioned under an absorbent material of the diaper. Each of the foil has an inner end located in the diaper, and an outer end protruding from lateral side of the diaper. The control unit has two end conductors, and a circuit electrically connected to the end conductors. The control unit is detachably fitted on the diaper with the end conductors electrically connected to the outer ends of the foil. The circuit and the foil are completed by urine of the diaper flowing into the absorbent material to activate a load of the circuit to alert the attending person.