A process comprising the first step of reacting a phosphorus oxytrihalide with a bisphenol A derivative at a specific ratio to prepare a phosphorohalidate, the second step of removing unreacted phosphorus oxytrihalide, the third step of reacting the reaction product obtained in the second step with a monophenol at 120°C or below, and the fourth step of reacting the phosphorohalidate with a monophenol at 120°C or above. The condensed phosphoric esters obtained by this process are extremely lowered in the content of isopropenylphenyl diphenyl phosphate, which is causative of a lowering in the heat resistance of a resin and staining of molds occurring in molding a resin, when the condensed phosphoric ester is used as an additive for the resin.