The present invention relates to aheat-dissipating device, which comprises an upper part and a lower part. The upper part further includes an inner joining face and an outer face opposite the inner joining face and the lower part further includes a concave surface which is engaged with the inner joining face of the upper part to form an air-tight chamber with a suitable quantity of circulating liquid being filled therein. The concave surface of the lower part further includes a plurality of capillary trenches and at least one basin, wherein each capillary trench connects the basin and further grid-like trenches are formed inside the basin in order to enhance vaporizing efficiency of the circulating liquid.