The general costs of an alum plant are analyzed using pilot plant test data gathered in 1994. The raw material used was typical kaolin from Cicalengka, West Java. The analysis is based on the plant capacity of 10,000 ton raw material of kaolin per day to produce 28,893.807 ton alum per year. It is found that the investment required is IDR 4.3 billion of which 65% was obtained from a bank loan. Production cost was IDR 308/kg of alum, while the selling price was IDR 112 higher than the production cost. The payback is expected to happen within 3 years with an internal rate of return of 25,56%. This cost evaluation however at the time of presentation may have altered due to inflation.