Thin films of III-V compound semiconductors, InSb and GaAs, are prepared using the ionized-cluster beam deposition. Thin films of InSb are deposited on (0001) sapphire by using a single ion gun. Substrate temperature is varied from 350-450°C, and an ion accelerating voltage from 0 to 6 kV. The improvement in crystalline quality with the ion accelerating voltage is observed through X-ray rocking curves. The best crystalline quality is obtained in the experiment with the deposition condition of 400°C (substrate temperature) and 4 kV (ion accelerating voltage). The film prepared with this condition shows the (111) -oriented twin crystalline. Thin films of GaAs cannot be prepared with a single ion gun, since the difference in the vapor pressure of Ga and As is so great that simultaneous deposition of Ga and As cannot be expected. Thin films of GaAs can be prepared on (0001) sapphire and on (001) Cr-doped GaAs by using two ion guns, each for Ga and As, in which the crucible temperatures are chosen to obtain the vapor pressure of As being 20 times to that of Ga. Substrate temperature is varied from room temperature to 700°C, and an ion accelerating voltage is varied from 0 to 6 kV. Again, the improvement in crystalline quality with the accelerating voltage is observed through high energy electron diffraction and photoluminescence.