Glucoamylase (EC 3.2.1.3. from Aspergillus niger) which is widely used in industry was immobilized directly in one step onto low-cost magnetic poly(styrene) particles including active groups. Glucoamylase in both free and immobilized forms was used to hydrolyze maltose. For both forms, the temperature of 50 degrees C and pH 4.5 were found as the optimum conditions in the aspects of activity and stability. Kinetic parameters were determined for the hydrolysis of maltose by free and immobilized glucoamylase at the same conditions in the batch reactor The,maximum activity obtained with immobilized glucoamylase is approximately 70% of the free one. The activity half lives Sor native and bound states of enzyme were found as 33.8 h and 190 h, respectively.