A process for preparing a phosphoric ester, comprising: Step (1) of reacting naphthol with phosphorus oxychloride in a molar ratio of 1:1.3 or more in the presence of a metallic halide and removing unreacted phosphorus oxychloride and Step (2) of reacting the reaction product of Step (1) with phenol in a molar ratio (molar ratio of chlorine contained in the reaction product to phenol) of 1:1 1.5 and removing hydrogen chloride produced as a by-product to thereby obtain a phosphoric ester represented by the general formula (I): ##STR00001## wherein n is 1 or 2.