To obtain a modified starch having excellent film-forming properties and paper improved in blister resistance by using the modified starch as a sizing agent and a coating agent.

This modified starch can be obtained by treating a raw starch or a modified starch prepared by modification such as enzymic treatment, grafting, etherification and oxidation in an alcoholic solvent at 100-150°C under pressure. Thereby, the film-forming properties, transparency, breaking strength and breaking elongation are improved. The modified starch is used as a binder, a sizing agent or a coating agent in the manufacturing industry such as papermaking, textile or corrugated boards to thereby improve the blister resistance at the time of printing.