To give flexibility to design and work execution of a semi-container case by forming a leaked gas discharging device for gas container, especially semi-container case, for LPG automobile and CNG automobile of the material having flexibility and air-tightness.

In a semi-container case A, a gas container side fitting port 2 is connected to a discharge port provided in a floor plate 5 of the interior C of an automobile. A master valve 7 of a gas container B and an operating handle thereof are housed in a case main body 1, and arranged inside of the interior over from a gas container neck part 4 to the discharge port of the interior C, and pipeing 9 is inserted into an inner space 1a of the case A and drawn out of the interior C from the discharge port. At this stage, the case main body 1 is formed into a hollow body having each gas container side and car side fitting port 2, 3 made of raw material such as rubber, which has flexibility and airtightness and durability against CNG or LPG. With this structure, flexibility of design is improved, and cost is lowered.