Activated carbon is widely used in various applications. It can be produced from natural sources having carbon content including corncob waste. This study aims to make activated carbon from the corncob waste. The effect of types of activators and activation temperature on the specific surface of the activated carbon was investigated. The experimental stages involved preparation, carbonization, activation, and sample analysis. During activation, the types of activators and temperature activation were varied, i.e. HNO3, HCl, H2 SO4, NaOH, all with concentration of 10% (mass), and variations in temperature of 70°C, 90°C, 110°C. The specific surface of activated carbon was determined with the methylene blue adsorption method using UV-Vis spectrophotometer. The results showed that the activation using 10% NaOH at a temperature of 110°C had the highest specific surface, i.e. 21.876 m2/g.