The objective of the research study was to determine the effect of ozonising raw juice obtained from sugar beet on its chemical composition and microbiological contamination. The research material were samples of raw juice from sugar beets harvested during a 2014 sugar campaign. The following parameters of the ozonation process of raw juice were applied: time: from 5 to 30 min; flow of ozone: 1.0; 4.5, and 7 dm³·min^-1; temperature of juice: approx. 18 ºC; sample volume: 500 ml. The ozone concentration in the mixture of air and ozone was 11 mg·dm-3 on average. The research showed that the ozone applied in a dose of 7 dm³·min^-1 reduced the count of mesophilic bacteria by 4 log, the count of slime-forming bacteria by 3.3 log, the count of yeast by 2.6 log, the count of thermophilic aerobic spore-forming bacteria by 1.2 log, and the count of moulds by 0.5 log. A statistically significant (p ≤ 0.05) difference was confirmed only in the case of the count of mesophilic bacteria where the application of ozone in a dose of 7 dm³·min^-1 lasted 30 min. No effect of ozone was confirmed on the content of the following ingredients in the raw juice: dry matter of sucrose, mineral compounds in the form of ash, nitrogen compounds, and metals: Na and K. Changes were found in the case of the content of reducing compounds (invert sugar), acidity, and colour. The maximum decrease in the intensity of the juice colour was 35 % when ozone was applied in a dose of 7 dm³·min^-1 during 30 min. period. The reduction in the acidity was 52 % for the ozone dose of 4.5 dm³·min^-1 during 20 min. lasting ozonation. The application of ozone in a dose of 1.0 and 7.0 dm³·min^-1 during a prolonged 30 min. lasting ozonation period did not significantly impact the decrease in the acidity of raw juice. The content of reducing compounds decreased 44 % during 20 min. ozonation at a gas flow rate of 4.5 dm³·min^-1.