Abstract. The conversion of Callophylum inophyllum L. oil into biodiesel using CaO catalyst from the shell of ale-ale (Meretrix-meretrix) in microwave-assisted reactor catalyst through transesterification has been carried out. The transesterification process was carried out using the ratio of moles of methanol/oil, the amount of catalyst, the variation of time, and the variation of the weight of the catalyst. The results showed that the optimum biodiesel obtained was at a mole ratio of methanol/oil 1:15, the amount of catalyst was 4%, the variation of time was 60 minutes, and the variation of
temperature was 65 oC. In the transesterification reaction, the optimum biodiesel produced from Callophylum inophyllum L. seed oil with a reaction time of 60 minutes, 4% catalyst weight, reaction temperature of 65 °C and a ratio of 1:12 methanol oil with the amount of biodiesel produced is 40.63%.