Indium tin oxide (ITO) is a solid solution of indium (III) oxide (In 2 O 3 ) and tin (IV) oxide (SnO 2 ). It is a typical object for research in modern optoelectronics. This material combines high transparency (in the visible) and conductivity simultaneously. It is used in the production of transparent electrodes of liquid crystal screens and solar cells. The optical properties of thin films of ITO were investigated using ellipsometry. Optical constants of these films were calculated using obtained ellipsometric parameters. Films thicknesses are equal to 21-34 nm, and their refractive indices vary in interval of 2,05-2,12. Also, it was found out how the deposition conditions of ITO films influences their optical properties.