A method for manufacturing a semiconductor package and the semiconductor package are provided. The method for manufacturing a semiconductor package may include arranging a conductive elastic plate over a package substrate including through slits disposed along edges of a chip mounting region and a conductive guard rails providing a concave trench shape, and bending the conductive elastic plate. Edge portions of the conductive elastic plate may be inserted into the trenches of the conductive guard rails and supported by the conductive guard rails by a force trying to stretch by the elastic restoring force of the wing portions of the conductive elastic plate.