A sunlight collecting device provided in the present invention includes a lens substrate, a plurality of Fresnel lens, a connector substrate, a plurality of optical fiber connectors, and a light-tracking substrate. The lens substrate has a plurality of circular openings. The Fresnel lenses correspond to the circular opening and are disposed on the lens substrate. The connector substrate is disposed parallel to the lens substrate and away from the lens substrate with a focal length. The optical fiber connectors are adjustably disposed on the connector substrate. The light-tracking substrate is disposed between the lens substrate and the connector substrate for simultaneously rotating the lens substrate and the connector substrate such that the Fresnel lenses are directly opposite to the sunlight. An LCD using the sunlight as a backlight source is further provided in the present invention.