The alarming device of the present invention includes a battery power supply; a sensor section that outputs an anomaly detection signal in the case of detecting an anomaly; a alert section that outputs an anomaly alarm based on the anomaly detection signal; a reception circuit section that receives an event signal from another alarming device; a transmission circuit section that transmits an event signal to the other alarming device; an anomaly monitoring section that, when the sensor section has detected an anomaly, causes the alert section to output the anomaly alarm based on the anomaly detection signal and causes the transmission circuit section to transmit an event signal according to the anomaly of the alarming device to the other alarming device, and on the other hand, when the reception circuit section has received an event signal according to an anomaly of the other alarming device from the other alarming device, causes the alert section to output the anomaly alarm; and a communication control section that detects a predetermined event and performs communication control by adjusting the transmitting and receiving of an event signal by the transmission circuit section and the reception circuit section.