The object of this invention is to improve safety by preventing the leakage of liquid caused by the internal pressure of a container. A liquid path plug in which a pipe is provided in the lid section of the plug, and a gas path plug which does not have a pipe are attached to openings of the container. The engaging groove section is formed on the end surface of the liquid path cap which closes the through hole provided in the liquid path plug section of the liquid path plug. The engaging protrusion section and the engaging hole section are formed on the end surface of the gas path cap which is provided in the gas path plug section of the gas path plug and closes the through hole. The gas path cap is detached by engaging the engaging pin of the detaching fixture on the engaging hole section of the gas path cap and by turning the gas path cap. The liquid path cap is detached by engaging the engaging protrusion section of the detached gas path cap on the engaging groove section of the liquid path cap and by turning the gas path cap.