Post-treatment of reduced copper catalyst, which contains Zn, Zr, and Al, with alkaline solution is effective in improving the selectivity to ethyl acetate in the dehydrogenative dimerization of ethanol. The treatment with Na2CO3 and K2CO3 greatly suppressed the formation of by-products such as butanone and 2-butanol, and resulted in the improvement of the selectivity to ethyl acetate. The suppression of butanone and 2-butanol is caused by the neutralization of surface acid sites that are active for the dehydration from 1,3-butanediol, into which acetaldol is hydrogenated. These acid-sites are formed after reduction of the Cu-Zn-Zr-Al-O mixed oxide precursor, and thus the post-treatment is effective. We also discuss the reaction routes in the side reactions. (C) 2004 Elsevier B.V All rights reserved.