To provide a failure diagnosis system capable of easily diagnosing a failure without installing a communication means and the like in not all the devices and readily applicable to an existing device.

This failure diagnosis system for a disaster prevention device is provided with the disaster prevention device, a circumstance display means installed in the disaster prevention device, a photographing means capable of photographing circumstances displayed by the circumstance display means, a communication means transmitting an image captured by the photographing means to a server, and a processing means determining a status of the disaster prevention device from the image transmitted from the communication means to the server. The processing means previously stores a normal image displayed in the circumstance display means for each disaster prevention device. When a failure state of the disaster prevention device is diagnosed by comparing the normal image displayed in the circumstance display means with the image transmitted by the communication means by the processing means, failure diagnosis can be carried out easily even if a communication means and the like are installed in not all the devices, while application to an existing device is carried out readily.