To provide a knit fabric developing shape memory property by heat-treatment, enabling recovery of the deformation of the fabric caused by the wearing for a long period, formable by three-dimensional forming if necessary, having high stretchability and excellent recovering property and most suitable as a women's inner wear.

The highly stretchable knit fabric is composed of a non-elastic filament fiber and an olefinic elastic yarn. The highly stretchable knit filament fabric having a constant load elongation of ≥50% in the direction of the polyolefinic elastic yarn, a recovery of ≥50% and an iron shrinkage of ≤5% is produced by uniting a polyolefinic elastic yarn under drafting with a non-elastic filament fiber and knitting the composite yarn singly or in combination with other non-elastic filament fiber yarn with a circular knitting machine.