A process for producing an esterificated condensate, wherein a monomeric ester or thioester, or a polyester or polythioester is produced by carrying out a direct condensation reaction from a carboxylic acid and an equimolar amount of an alcohol or a little excess amount of a thiol in a non-polar solvent such as toluene using, as a (poly)condensation catalyst, a tetravalent hafnium compound, typically, hafnium(IV) chloride, in particular hafnium(IV) chloride . (THF)2 and hafnium(IV) butoxide in an oxygen-free atmosphere under reflux. During refluxing with heating, water being distilled as an azeotropic mixture is preferably removed from the reaction system. The process permits a catalytic esterification using equimolar amounts of a carboxylic acid and an alcohol and a catalytic thioesterification using a carboxylic acid and an equimolar or a little excess amount of a thiol, and accordingly is greatly promising as a commercial process for a large scale production from the view point of green chemistry.