The manufacturing process of vegetable oil based biodiesel was introduced in experimental manner. Ultrasonic energy was irradiated to induce the transesterification of the vegetable oil. The ultrasonic irradiation had two effects, those were heating and mixing of the reactants. We performed the experiment under various manufacturing parameters, viz. the ultrasonic irradiation time, sonic power, and irradiation type at constant reaction temperature, 55℃. The ultrasonic irradiation biodiesel synthetic process reduced the reaction time by 30 min or more comparing to existing processes. The ultrasonic energy densities (Ua) were calculated from the experimental data. The highest yield and methyl ester content were observed at an ultrasonic power of more than 450 W. The reaction conditions were also adjusted to stabilize the reaction media temperature.