To immediately ring a buzzer when bedding are taken away during sleep and to signal to a monitoring person about it by attaching sensors to certain suitable contact parts of a quilt and a reference object.

A transmitter 1 and a receiving signaling device 6 are separately and independently constituted, and sensors (1) 3 and (2) 4 are plug-in-type position moving sensors and are connected to the transmitter 1 through wires 5. When they are used, the transmitter 1 is arranged around the head of a bed of a monitored person (child, etc.), the sensor (1) 3 is attached to a top outside of a quilt and a reference object on an installment side of the transmitter 1, and the sensor (2) 4 is attached to the top outside of the quilt and a mattress which are opposite when a bedding on an installment side of the transmitter 1 is a center with a wire passed through under the reference object. The device 6 is installed at the head of a bed of a monitoring person. Thereby, when the monitored person takes bedding away and is away from the monitoring person, a buzzer of the device 6 notices it.