This paper presents the first comprehensive study of the anodic oxidation process of GaSb. Acid-glycol-water electrolytes in a wide range of pH values were investigated. Dependencies of the thickness, refractive index, and homogeneity of anodic oxides on the applied voltage, starting and final current, pH value of the electrolyte, content of ethylene glycol, and thr surface quantity of the samples were determined. Anodic oxides of GaSb were studied by monochromatic and spectroscopic ellipsometry. For the first time the refractive index n of anodic oxide was determined in a wide wavelength range of 400-1700 nm.