The present invention aims to present methods to detect nonalcoholic fatty liver disease including nonalcoholic steatohepatitis by using a protein or its partial peptide that differs in presence or absence, or in quantity between healthy human subjects and patients with nonalcoholic fatty liver disease or nonalcoholic steatohepatitis or between patients with fatty liver and nonalcoholic steatohepatitis and further aims to present biomarkers comprising said protein and said partial peptide to be used to detect nonalcoholic fatty liver disease including nonalcoholic steatohepatitis. Specifically, 35 kDa protein fragment consisting of amino acid sequence expressed by Sequence No. 2 and its partial peptide consisting of amino acid sequence expressed by Sequence No. 3 (including its glycated form) of inter-alpha-trypsin inhibitor heavy chain H4 precursor consisting of amino acid sequence expressed by Sequence No. 1 could be used as biomarkers to detect nonalcoholic fatty liver disease including nonalcoholic steatohepatitis.