Abstract: The present invention covers 2-aminoethanesulfonic acid zinc complex compound as represented by the formula [I]: ##STR1## as well as a process for producing the same, and an anti-hepatitis agent, liver function improving agent and anti-ulcer agent. As compared with 2-aminoethanesulfonic acid, glutathione and glycyrrhizin, the compound (I) of the present invention exhibits improved anti-hepatitis activity, and also strengthens detoxicating activity toward various compounds to thereby develop liver function improving activity, while the said compound shows excellent anti-ulcer activity but greatly lowered toxicity.