Abstract: A sealing cap for the mouth of a container facilitates both the sealing of new bottles containing unused contents, and the re-sealing of those bottles already in use so as to preserve their contents. The sealing cap includes an inner cap and an outer cap. The inner cap includes a shielding plate which is fixed on the mouth of a container, and an annular strip which is provided at the lower end of the outer circumferential wall of the inner cap. The outer cap, which is fixed on the inner cap, includes a top lid, and a main cap with a guide tube having a lower-end sharp edge located opposite the shielding plate. By removing the annular strip from the inner cap and pressing down the outer cap, the lower end of the outer cap engages the outer circumference of the mouth of the container, and at the same time, the lower-end sharp edge of the guide tube pierces the shielding plate. The user then opens the top lid of the outer cap to access the contents of the container.