Molecular change of starch granules and its reaction in the simple system with heat in the cases of 11 starch species (normal-, amylo-, waxy-maize, normal-, waxy-wheat, normal-, waxy-rice, potato, sweet potato, cassava, sago) were studied . Dry heat treatment of starch samples was carried out at 200°C for 0.5 h, 1 h and 2 h. Oil treatment involved heating of starch in soy bean oil, methyl laurate and methyl oleate and kept at 190°C. After heating, SEM showed no changes of the granule images but they became instantly water soluble after 2 h heat treatment. GPC studies revealed that every 2 h starch sample was largely disrupted and became smaller than amylose but fairly larger than oligosaccharide. Hence, one assumed that starches are disrupted to cluster unit. Decomposition ratio of amylose was different among plant origin. In general, tuber starch was far more resistant to heat than cereal starch. Oligosaccharides formed in this processing are all anhydro type. Heat treatment in oil gave almost same effect on starch and the decomposition took place more rapid than in air. However, treatment time did not bring increase of oil incorporation into starch granule and there was little difference among oil species.