A reflectance measuring apparatus is provided in the present invention. In addition to measuring the intensity of light directly reflected from a sample, the apparatus is further capable of collecting large-angle reflected light scattered from the sample through a reflecting cover disposed over the sample and measuring the intensity thereof. In one embodiment, the reflecting cover has a parabolic surface for modulating the large-angle reflected light to become parallel light projecting onto a photo-detector. In another embodiment, the reflecting cover has an elliptic surface for modulating the large-angle scattered light to focus on the photo-detector.