A heat-dissipating device with an isothermal plate assembly of predetermined shape and method for manufacturing the same are proposed. An upper plate and a lower plate with predetermined shape are provided and an accommodation groove is defined therein. A flattened heat pipe is bent into the predetermined shape and placed into the accommodation space. A binding agent is applied on the face between the heat pipe, the upper plate and the lower plate. A heat-dissipating unit composed of a plurality of heat-dissipating fins is assembled to a concave portion of the isothermal plate assembly of the predetermined shape. The upper plate and the lower plate are assembled with outer coupling unit and then a hot melting process is executed. The resultant product is then cooled to form a finished heat-dissipating device with an isothermal plate assembly of predetermined shape.