To provide a wet diaper sensing and informing system which can inform a person away from a diaper user that a diaper is wet, and has a simple structure of a wet diaper sensing portion.

The system is equipped with a wet diaper sensing portion 110, a transmitting device 130 connected to the wet diaper sensing device 110, and a receiving device 140 to receive a signal transmitted from the transmitting device 130. The wet diaper sensing portion 110 is equipped with a rigid insulating bag 111, a stretchable insulating partition film 112, a water-absorbing/swelling member 113, an inner periphery surface 114 for urine to run through to define a urine running hole 1141, and switch terminals 115 and 116. The transmitting device 130 is equipped with a means to send a wet diaper signal to indicate that the diaper is wet, when the switch terminals 115 and 116 are brought into contact with the wet diaper. The receiving device 140 is equipped with a means to indicate wetting of the diaper after receiving the wet diaper signal.