The In2Oa-SnO 2 binary system between 1473 and 1873 K has been investigated bY TEM observations in detail. The intermediate compound has been detected above 1573 K in the composition range from 47.9 to 59.3 mol % SnO2, that crystal structure is long range ordered cubic system similar to In203 phase. On the other hand, below 1473 K, the intermediate compound is decomposed into In203 and SnO2 phases, according to the eutectoid reaction.