The improvement of grain quality is an important breeding objective. Mutation techniques have proven their potential for generating useful variability in plant breeding. In order to obtain genetic materials to breed qualitatively improved rice storage proteins, we screened about 144 mutant lines induced by the treatment of mature seed with sodium azide. The screening was performed by comparing the profiles of sodium dodecyl sulfate polyacrylamide gel electrophoresis with that of the original variety, Suweon 472. With some exceptions, we have been able to select lacking or decreased mutant lines for each of the bands of major proteins with molecular weights of 80 kDa. Electrophoretic analysis of glutelins revealed that the range of 97.4 kDa and 45 kDa were considered as subunit variation occurrence region. Selected 13 glutelin mutant lines were classified into 3 types on the basis of variations of the relative contents of the polypeptides. Treatment of the mature seed with sodium azide was found to be an effective method to induce mutations for storage proteins in protein bodies of rice. The use of SDS-PAGE techniques has enabled the arranging of a system by which the changes in the various seed storage protein components can be extracted and detected in a relatively simple manner and the selection of seed storage protein mutants has been facilitated by a method in which the endosperm of the M3 seed is examined directly. The biochemical clarification of the properties of glutelins proteins in the endosperm has enabled selection of mutants based on breeding goals and aimed at composition. Immunoblotting experiment, using anti-waxy polyclonal antibody (AWPab), confirmed that rice GBSS was high homology to wheat GBSS. The biochemical clarification of the properties of glutelin proteins in the endosperm has enabled selection of mutants based on breeding goals and aimed at composition.