PROBLEM TO BE SOLVED: To provide a method for restricting occurrence of fish diseases in a simple method at lower cost than vaccination, since vaccines for cultivated fish are expensive, and vaccination is labor-taking, while spreading of fish diseases such as the Edwardsiella infectious disease has been a problem in culture farms.SOLUTION: Fermentation materials including vegetable materials and animal materials are fermented by use of a group of microorganisms including thermophilic bacterium of a plurality of kinds of living things to provide the functional culture feed having the function of restricting occurrence of fish diseases.