A fire detector which can be observed an operating state thereof from every direction and decrease a cost thereof as possible. The fire detector (10) comprises: the circuit board (32) in which the circuit for detecting a fire is formed; the LED (35) which is surface-mounted on the circuit board (32); and the indication lamp for indicating the fire detector being under detection by emitting the light emitted from the LED (35), wherein the indication lamp comprises the light guide member (20) for introducing the light emitted from the LED (35) to the indication lamp with a ring shape, the light guide member (20) comprises the light incident parts (21) and (21) and the ring member (22), notches (23) and (23) are formed in the vicinity of the light incident parts (21) and (21) of the ring member (22), and a plurality of small grooves (24), and (24) . . . are formed in the bottom surface (22d) of the ring member (22).