The present invention relates to a straight airtight valve comprising a primary valve body in which an opening/closing space are partitioned and which has an inflow passage formed from one side end to communicate with the opening/closing space and an operable passage from the other side end facing the inflow passage on the same axis to communicate with the opening/closing space; an adjusting screw which is coupled and fixed to be able to rotate at an end of the operation passage of the first valve body; and an opening/closing rod which includes a side of a bar-shaped operable unit, which is screwed to be able to move on a straight line by the adjusting screw, extended and inserted into the opening/closing space via the operable passage of the first valve body, an opening/closing unit formed at an end of insertion side the opening/closing space of the operable unit and configured to open or close the operable passage, and a discharge passage formed from the opening/closing unit along an axis direction within the operable unit to be communicated with the opening/closing space. According to the present invention, the volume of a valve in an axial direction is reduced by removing a handle portion from the valve controlling a fluid flow, and accordingly, the volume of the tritium container can be reduced. Therefore, the second packaging of the tritium container can be easier, and a gas leakage can be minimized through a switch portion of the valve even when the valve is opened as well as closed.