Abstract: A fire alarm system according to an embodiment of the inventive concept includes a plurality of sensing systems, each sensing whether a fire has occurred, and a plurality of relay systems each corresponding to any one of the plurality of sensing systems, performing Radio Frequency (RF) communication with the plurality of sensing systems, and performing RF communication with each other, wherein each of the plurality of sensing systems includes a plurality of sensing units having different address information, wherein when detecting a fire, each of the plurality of sensing units transmits alarm information to a corresponding relay system among the plurality of relay systems, wherein when receiving alarm information from another adjacent sensing unit, each of the plurality of sensing units transmits the alarm information to a corresponding relay system among the plurality of relay systems, wherein each of the plurality of relay systems includes a memory in which information of parties corresponding to the addres