Disclosed is a nonhuman animal showing the symptoms of human nonalcoholic steatohepatitis which is obtained by transplanting human hepatocytes into an immunodeficient hepatopathic nonhuman animal to produce a chimeric nonhuman animal and then transplanting human hepatocytes that are propagated in the body of the chimeric nonhuman animal into an immunodeficient hepatopathic nonhuman animal of the same species as the immunodeficient hepatopathic nonhuman animal described above, as well as a nonhuman animal showing the symptoms of human fatty liver which is obtained by transplanting human hepatocytes into an immunodeficient hepatopathic nonhuman animal to produce a chimeric nonhuman animal.