A device to detect defects in a finished surface by analyzing images thereof taken under lighting of different colors includes a supporting mechanism, a transmitting mechanism, a detecting mechanism, and a processor. The transmitting mechanism carries and transmits the product. The detecting mechanism includes a detecting frame, and a light source assembly. The processor connects to a camera assembly, and preprocesses images obtained of the long side surfaces, of the width side surfaces, and of the chamfered side surfaces of the product to detect any defects of these surfaces of the product.