Biodiesel can be produced from various oils and fats. Due to possibility of diversion of edible oils from feed stocks to raw materials for biodiesel production, which may lead to food crisis, it is preferable to choose non-edible oils as raw material for biodiesel production. As a country rich in natural resources, Indonesia has a vast amount and variety of non-edible fatty-oil production plants. However, non-edible oils usually have high free fatty acid (FFA) contents. Oils with high FFA contents cannot be converted directly to biodiesel using a conventional alkaline catalyzed process due to saponification problem. To avoid this problem, the high FFA contents in the oils must be reduced via esterification process using acid catalyst. The use of homogeneous acid catalyst in this process can be very corrosive and not environmentally friendly while the use of commercially available heterogeneous acid catalyst can be very expensive. In this research, a heterogeneous acid catalyst suitable for biodiesel production will be derived from corn starch through pyrolysis followed by sulphonation processes. The purpose of this research is to study the effects of pyrolysis temperature and time to the acid density of the catalyst and the activity of the catalyst in the esterification of oleic acid using a 22 factorial design with 3 center points experimental design. It is found that the catalyst obtained from pyrolysis at 400°C for 15 hours has the optimum–HSO3 content of 5.9% which corresponds to the highest average conversion of the esterification of oleic acid of 97.45%.