Nowadays, the increasing need for energy fuels threatens up to the extinction of fossil fuels and increases pollution. Therefore, it is necessary to develop alternative energy that is environmentally friendly and easily produced such as biodiesel. Biodiesel can be produced from substances that contain fatty acids through transesterification reaction with alcohol and base catalysts. In this study, used waste cooking oil is used as a source of fatty acids and CaO catalysts synthesized from duck eggshells and chicken eggshells. The result shows that the transesterification reaction worked optimally with 5 % weight of catalyst, 600 W of microwave energy, 40 seconds of reaction time and methanol to oil molar ratio of 1:15. The biodiesel products obtained were characterized by gas chromatography-mass spectrometry (GC-MS) and were a methyl ester compound such as methyl palmitate, methyl stearate, methyl 9-octadecenoate, methyl 2-hydroxy hexanoate and hydroxypropyl methyl oleic.