A water-soluble film is provided that is capable of achieving deformation resistance during pouch storage as well as excellent water solubility of the film and excellent reduction in undissolved residues. A water-soluble film includes a polyvinyl alcohol-based resin, wherein a crystal long period Ds obtained from an X-ray profile obtained by small-angle X-ray scattering measurement in a water/methanol mixed solvent (volume ratio: 2/8) is from 10.0 to 30.0 nm and a rate of increase (DS−Da)/Da of the crystal long period Ds to a crystal long period Da obtained by small-angle X-ray scattering measurement before immersion in the solvent is 30% or more and 130% or less.