To obtain a three dimensional knit fabric for airtight structure base fabric having good morphological retention and to provide its production method in high production efficiency.

This knit fabric is a three dimensional knit fabric having front- back two knit fabrics jointed with inexpensible joint threads at intervals and having plural sections where inexpensible joint threads are crossing each other. The three dimensional knit fabric comprises jointing a surface knit fabric (a) with a rear knit fabric (b) at selvedges of both ends and boundaries of the section. The production method of airtight structure base material comprises forming sheets of impervious layers at front and back surfaces of each of the front side knit fabric (a) and the back side knit fabric (b), cutting the resultant at combining part of the selvedges of the section and making the cut part to be airtight.