PURPOSE:To obtain a water-soluble film which can retain excellent water solubility for a long time in contact with an alkaline or acidic substance and has suitable touch and flexibility by using a specified 2-pyrrolidone ring-containing polyvinyl alcohol. CONSTITUTION:This water-soluble film is formed from a 2-pyrrolidone ring- containing polyvinyl alcohol containing 120mol% 2-pyrrolidone ring-containing copolymer units in the molecule and having a degree of saponification of 50-99mol%. As the 2-pyrrolidone ring-containing copolymer unit, one containing a group of formula 1 (wherein R1, R2, R3, R4, R5 and R6 are each a hydrogen atom or an alkyl) is desirable. Especially, one in which all of R1-R6 are hydrogen atoms is desirable. A water-soluble film can be produced economically by melt- molding the above 2-pyrrolidone ring-containing polyvinyl alcohol in the substantial absence of water.