To obtain a water-soluble film that is excellent in cold water solubility and is useful as a chemical agent package, provided is a water-soluble film, which is a polyvinyl alcohol water-soluble film including a carboxylic acid-modified polyvinyl alcohol resin (A) as a main component, wherein a lactonization rate of a carboxylic acid modifying group in the carboxylic acid-modified polyvinyl alcohol resin (A) is from 20% to 70%.