An illuminated logo unit (300) includes an image panel (301), and an underlying illuminating device (310) transmitting light beams to the image panel. The illuminating device includes an inner discoid light guide plate (312) fitted into an outer annular light guide plate (311), and four light sources (369, 359) separately emitting light beams toward respective emitting surfaces (360, 350) of the light guide plates. A reflective film (362) coated on a circumferential wall (361) of the inner light guide plate prevents light beams in each light guide plate from interfering with light beams of the other light guide plate. A reflective film (352) coated on a circumferential wall (351) of the outer light guide plate prevents light beams from leaking thereout. By the use of the light guide plates, the illuminated logo unit attains uniform illumination in each of two illumination areas thereof.