An electronic device for optically detecting an appearance of a product for defects includes a first camera device, a second camera device, at least one white light source, and at least one red light source. The first camera device is perpendicular to a plane of the product to be detected. When the red light source is activated, the first camera device captures images of edges of the plane of the product, when the white light source is activated, the second camera device captures images of the plane of the product. The electronic device detects the appearance of the plane of the product for defects according to the images captured by the first and second camera devices, the defects can include stair slope errors, scratches, sanding marks, and gas marks.