To provide a inflation film and its manufacturing method excellent in low odor characteristics, low taste migration, heat stability, and mechanical properties.

An inflation film is manufactured by an ion polymerization method. A density is 0.89-0.96 g/cm3, and a melting viscosity η* [170] is from 0.001×104 to 3.5×104 poise at 170°C and at a shear rate of 100 rad/sec. An ethylenic polymer or a resin composition containing the ethylenic polymer having a weight ratio (a) (wt.%) of a soluble matter of a cold xylene satisfying an expression: a <4.8×104×(0.95-d)3-+106×(0.95-d)4+0.5, where (a) represents the weight ratio (wt.%) of the cold xylene-soluble portion, and (d) represents a density (g/cm2) of the ethylenic polymer, is processed in a die gap at a melting temperature of 170°C or lower.