An industrially useful process for producing benzofuran derivatives of formula (1): ##STR1## by formylating a compound of formula (2): ##STR2## (where A.sub.1 is a protective group), followed by reaction with a compound of formula (4): ##STR3## (where X.sub.1 is a halogen atom), then performing a cyclizing reaction and subsequently performing a reaction for hydroxyl group deprotection.
