Using the protein chip technology, biological samples such as sera are subjected to proteome analysis. Thus, a protein which is a human fibrinogen .alpha.-E chain decomposition product and has a molecular weight of 5,900, a protein which is an apolipoprotein AII decomposition product and has a molecular weight of 7,800, and a protein which is an apolipoprotein AI decomposition product and has a molecular weight of 28,000, each showing an increase or a decrease with the habit of drinking, are newly found out. By detecting or quantifying these proteins, a liver disease in a subject such as one having a problem of drinking can be diagnosed at the early stage.