An illuminating device having folding solar panels, which comprises a lamp cover, a light source, two solar panels, and a folding holder on which the two solar panels are positioned. The opening of the lamp cover is smaller than the deployed area of the folding holder. When it is intended to place the light source, solar panels, and folding holder inside the lamp cover, the folding holder are folded by a predetermined angle so as to pass through the opening of the lamp cover. Accordingly, the illuminating device may significantly reduce the overall volume thereof without compromising the working efficiency. The illuminating device is flexible in arrangement and assembly, and is also more flexible in construction since the solar panels may be positioned at the highest portion to absorb more sunlight.