A printed wiring board includes at least one insulator sheet having through holes filled with conductive material and a conductive wiring pattern. The wiring pattern is embedded in the insulator sheet so that an upper surface of the wiring pattern and surrounding portions of the insulator sheet form a flat surface. The insulator sheet may be made from a glass-epoxy prepreg or of a polyester or polyimide sheet coated with an adhesive or glue. The wiring pattern can be transferred to the insulator sheet from a surface of a releasable supporting sheet.