To provide an aqueous composition of a graft modified starch obtained by a series of processes of gelatinization, addition reaction and graft reaction of a starch without the need of refinement, the aqueous composition obtaining a colorless film with a preferable viscosity stability in an aqueous solution state and a high water resistance even if a composition derived from a starch is included by a large amount.

The aqueous composition of a graft modified starch with the crystallinity derived from the starch remaining is obtained by cutting the starch chain by dropping a monomer-emulsified product made of one or more ethylenically unsaturated monomers and an oxidizing agent in the presence of a starch with its α (gelatinization) degree controlled, and carrying out graft polymerization reaction of the ethylenically unsaturated monomer to the starch at the same time.