Transesterification of waste cooking oil (WCO) using NH2/MCM-41 base catalyst has been carried out. The MCM-41 was synthesized by hydrothermal method using the silica from Sidoarjo mud and cetyltrimethylammonium bromide (CTAB) as a template and calcined at 540 °C for 5 h. The MCM-41 was modified by adding (3-aminopropyl) trimethoxysilane using 5 mol percent of N/Si to produce NH2/MCM-41 base catalyst. Transesterification of waste cooking oil was carried out under variation of methanol/WCO mole ratio of 6, 9, 12, 15 and 18 using 10 wt. % of catalyst towards oil and weight ratio of catalyst/WCO of 2, 4, 6, 8, 10 wt. % using methanol/waste cooking oil mole ratio of 15. The result showed that the purity of silica from Sidoarjo mud was 93.40 wt. %. The highest product of methyl ester was 49.98 wt. % obtained using 4 wt. % of catalyst/WCO weight ratio in methanol/oil mole ratio of 15.