Long-term stability is a key property of enzyme membranes that can be used for biosensors, bioreactors, and bio-fuel cells. This review discusses factors that decrease the stability, and provides two examples of enzyme membranes, a polyion complex membrane and a cellulose membrane, with which stability loss can be avoided. By using these materials, long-term stability was improved. These supporting materials could be applied to construct biosensors, bioreactors, and bio-fuel cells.