SUMMARY In the modern world, due to growing environmental problems, there is a need to use renewable energy sources in everyday life and industry. Therefore, biodiesel, which is obtained by the transesterification reaction of alcohol and fats/oils of vegetable or animal origin, with the presence of a catalyst, competes over classical energy sources obtained from fossil sources. In this thesis, the influence of reaction parameters on the yield of the reaction between propanol and sunflower oil, with KOH as a catalyst, was investigated. Four parameters were examined: reaction temperature, time of reaction, mass fraction of catalyst and molar ratio of propanol:sunflower oil. The highest conversion of 99.79 % is achieved at the temperature of 60 °C, reaction time of 2 hours, propanol:oil ratio in the amount of 10:1 and the mass fraction of catalyst 1 wt. %. The design of the experiment was preceded by 3 preliminary experiments, where the temperature values were from 40 to 80 °C, time from 1 to 3 hours, propanol:oil ratio from 6:1 to 10:1 and a mass fraction of catalyst from 1 to 3 wt. %. Experiment planning and processing statistics were performed in the Design Expert software package. After the experiments, the optimization of the transesterification process was made, with the aim of achieving the highest possible conversion. Therefore, we strived for the shortest possible reaction time, lower temperatures, lower ratio of propanol and sunflower oil, and lower mass fraction of catalyst. Depending on the given importance of each goal (1-5), three cases with different optimal conditions were obtained. The selected optimal conditions were: temperature 40,00 °C, time 2,42 h, propanol:oil ratio 9,53:1, mass fraction of catalyst 1 wt. %, where the predicted yield is 96,81 %.