The present invention relates to a heterocyclic compound of the following general formula (I): ##STR1## wherein X is sulfur atom, oxygen atom or --NR.sup.3 -- (R.sup.3 may form a heterocyclic ring or a substituted heterocyclic ring with R.sup.1 via the nitrogen atom), R.sup.1 is alkyl group, substituted alkyl group, aryl group, substituted aryl group, heterocyclic group or substituted heterocyclic group, and R.sup.2 is hydrogen atom, halogen atom etc.; or its pharmaceutically acceptable salt and interferon inducers, antiviral agents, anticancer agents and therapeutic agents for immunologic diseases comprising the compound (I) or its pharmaceutically acceptable salt as active ingredients.