A smoke detecting device including: a light-emitting portion that emits light; a light-receiving portion that receives scattered light resulting from the light which the light-emitting portion emits being scattered by smoke generated from a recording medium on which flash-light is irradiated from a flash fusing device; and a judging section that acquires a light amount signal of the received light, from the light-receiving portion, and that judges, on the basis of the light amount signal, whether or not smoke has been generated from the recording medium on which flash-light is irradiated from the flash fusing device, the light that the light-emitting portion emits passing through a space between the flash fusing device and the recording medium, is provided.