An illuminating device includes: an illuminating board having a plate-like transparent board, a reflector provided on a back surface of the transparent board to reflect light, and a cloudy, translucent medium provided on a front surface of the transparent board; a support member supporting an end of the illuminating board in a cantilever fashion, so as to provide a free end for the other end of the illuminating board; a light emitting portion, arranged beside the supported end of the illuminating board, that emits light to the transparent board at the supported end; and an emission control unit that causes the light emitting portion to emit light.