To provide a reflection member and a fire sensor, capable of uniformly irradiating a predetermined region with a reflected electromagnetic wave.

In a reflection member, ultraviolet light reflected by a light source side edge 32a of an opening 32 on a light source side enters an edge 221a of one of two edges of an irradiation region 221 in an electrode 22, and ultraviolet light reflected by a light source side edge 32b of the other edge of the opening 32 on the light source side enters an edge 221b, and ultraviolet light reflected by a discharge tube side edge 33a of an opening 33 on a discharge tube 2 side enters the edge 221b on the discharge tube side of the irradiation region 221, and ultraviolet light reflected by an edge 33b of the other edge of the opening 33 on the discharge tube 2 side enters the edge 221a of the irradiation region 221. Accordingly, the predetermined region 221 of the electrode 22 is uniformly irradiated with the reflected ultraviolet light.