To provide a residual quantity displaying device for a gas container and its manufacturing method equipped with a display free of being bedewed.

The residual quantity displaying device 3 for the gas container is structured so that a container side magnet 6 is mounted on an operating rod 5 moving in compliance with the residual quantity of the gas in the container and also a displaying magnet 10 to move in follow-up after the container side magnet 6 is installed movably within the display 8. The display 8 is composed of a case 9 in cylindrical shape, a lid 13 to close tightly the opening in the case 9, the displaying magnet 10 installed in the case 9 movably, and a gas not containing water/moisture such as nitrogen gas which fills a sealed space 12 formed from the case 9 and the lid 13. The nitrogen gas etc. filling the space 12 is filled in the atmosphere of a sealed box.