Illipe butter is a product from Illipe nut, which is native from Borneo Island in Indonesia. This study aimed to analyze the effect of purification and lignin addition as a prospective natural antioxidant of Illipe butter. The purification process of Illipe butter consisted of degumming process, neutralization, and bleaching with the addition of activated bentonite. Magnesium lignosulfonate, calcium lignosulfonate, and sodium lignosulfonate as lignin derivatives were added at varied concentration of 1%, 2.5%, 5%, and 10% (w/w) into the purified Illipe oil to study their effect on its free fatty acid content. Beta-carotene level and free fatty acid content of both unpurified and purified Illipe butter were then analyzed according to SNI 2903-2016. The result showed that the purification process could decrease beta-carotene level of Illipe butter from 15.94 mg/kg to below 0.82 mg/kg which qualitatively could be seen in the change of Illipe butter's color from yellowish-green to yellowish-white after purification. Purification process also reduced Illipe butter's free fatty acid concentration from 9.04% to 3.32%. All types of lignin in this study could effectively reduce the free fatty acid content of Illipe butter. The most effective lignin derivative was sodium lignosulfonate where free fatty acid concentration could be reduced from initially 3.32% to 1.83% at 10% (w/w) lignin concentration.