A cover of an electronic device has a body inside and is penetrable by light yield from an illumination device. The body has an inner surface having a region impenetrable by light as a light-blocking region and the remaining region penetrable by light as a light-passing region. The body further has an outer surface having a region impenetrable by light as another light-blocking region and the remaining region penetrable by light as another light-passing region. The light-blocking region of the outer surface correspond to the light-passing region of the inner surface in shape, but in a size that is smaller, so that when light pass through the body, light can give an effect that the shape of the light-blocking region looks three-dimensional.