An exemplary optical guiding device for optically coupling a plurality of light beams having at least one laser beam, includes a light coupling lens, a light collimating lens, and an optical fiber. The light coupling lens and the light collimating lens are positioned apart along an optical path. The optical fiber is optically coupled to the light couple lens. External laser beam introduced by the optical fiber are optically coupled by the light coupling lens for collimating and mixing the light beams, then collimated by the at least one light collimating lens, and finally emitting out. A backlight module using the optical guiding device with colored semiconductor lasers and light transferring device are also provided. The backlight module has a good color performance, such as high color saturation.