In this study, transesterification activity of sunflower oil with methanol was tested over Amberlyst A-21 (A-21) and Amberlyst A-26 (A-26) type ion exchange resins which have high Hammett basic strength. Transesterification reactions were carried out in a three necked batch reactor at operating temperatures of 40 to 55 degrees C, methanol-oil initial molar ratio of 3: 1 to 6: 1 and 1% to 5% (of oil) weight percentages of catalysts. A-26 catalyst was determined to be more active than A-21, with a % 91 conversion at 50 degrees C and 6: 1 methanol-oil initial molar ratio. % 88 conversion was achieved with the same reaction conditions over A-21 catalyst. Experiments were designed by using Box-Wilson experimental design method. Experimental results were analyzed by using "Design Expert 126.96.36.199" program. Mass transfer limitations was not significant. An increase in temperature and initial molar ratio of reactants caused an increase in biodiesel conversion. Hammett basic strength of these two catalysts were found as H_> 9.8. Swelling behaviour of the polymeric structured catalysts was measured % 100 at all reaction temperatures.