Agglomeration-free indium oxide particles were produced by ultrasonic pyrolysis of indium nitrate(3 hy-drate) solution. Th mean size of particles was increased from 3 $mu extrm{m}$ to 11$mu extrm{m}$ with increasing intial con-centrations of indium nitrate from 0.05mol% to 4.83 mol% When the input rate of indium nitrate solution was increased from 0.1 cm3/min to 0.8cm3/min the size of particles remained same and only the pro-duction rate of particles was increased. At 300$^{circ}C$ the particles were white color with low crystallinity. But the color turned into yellow with increasing reaction temperature. The change of particle size was not ob-served with increasing temperatuer up to 700$^{circ}C$ IR spectrum and TGA analysis confirmed that the purity of indium oxide was increased with temperature of reaction.