PURPOSE: To modify starch without a problem of waste liquor disposal, by feeding starch to a reaction zone of a gas discharge plasma generator to a expose it to a gas discharge plasma.

CONSTITUTION: Starch is fed to a reaction zone of a gas discharge plasma generator to expose it to a gas discharge plasma in said reaction zone. The gas discharge plasma is a collection of ions electrons and neutral particles and can keep its state for a time several times longer than the mean collision time of the particles. In general, a low-pressure high-frequency discharge which can give easily a stable and uniform and an atmospheric corona discharge which requires no application of a vacuum and is advantageous in actual use can be used. The modified starch obtained by this modification process can be used in the production of foods such as cakes, noodles and fish-paste products, sizings for fibers and papers, drugs (glucose and vitamins), etc.