A molded casing suitable for a handheld electronic device is provided. The handheld electronic device includes a body and the molded casing, and at least one part of the body is covered with the molded casing. The molded casing is in a uniform thickness and has a continuous mosaic surface. The mosaic surface is composed of a plurality of non-coplanar polygons, wherein an intersection line is formed between any two adjacent polygons. An end of any one of the intersection lines is connected to an end of another intersection line or an edge of the mosaic surface.