Abstract: The present invention is a process for producing an oxetanyl group-containing cation-curable silicon compound where a hydrolysis co-condensation of (A) and (B) below is performed in the presence of an acidic catalyst in which pKa ?5 (25° C.) and boiling point ?150° C. (at atmospheric pressure); and is preferably a process for producing an oxetanyl group-containing cation-curable silicon compound where a hydrolysis condensation of (A), (B) and (C) below is performed in the presence of an acidic catalyst. wherein R0 is an oxetanyl group-containing organic functional group; X is a siloxane-bond-forming group; R2 is an alkyl group, a cycloalkyl group or an aryl group; n=0?2; and Y is a hydroxyl group or a siloxane-bond-forming group.