Longitudinal and transverse stretching of a tubular film is effected by gripping opposite selvages of the tubular film between a pair of substantially coplanar pulleys and a pair of endless belt means trained arcuately around the pulleys, respectively, and by rotating the pulleys at a peripheral speed greater than a speed of feed of the tubular film. As the film selvages progress along a pair of arcuate divergent paths, respectively, around the pulleys, the film is heated, reversed in direction of travel, and cut along the selvages into a pair of biaxially stretched sheets. Before stretching of the film, live steam is introduced into the tubular film for heating the same.