The waste oil adsorbed on activated bleaching earth was evaluated as a raw material for biodiesel production. Alcoholysis reactions of waste oil extracted from activated bleaching earth using n-hexane were conducted by NaOH as catalysts. The reactions were performed at a temperature range from 50 to 60 degrees C with catalyst (1-2% based on oil weight) at oil:alcohol molar ratios of 1:5-1:7. Based on optimization by response surface methodology, the critical alcoholysis conditions for 30 min reaction time giving maximum 85% methyl ester content were determined as follows: temperature 57.3 degrees C, catalyst 2.1% (based on oil weight), and oil/methanol molar ratio 1/6.3.