The present invention is to provide methods for producing highly pure 4,4'-dihydroxydiphenyl sulfone monoethers advantageously in industrial production.In a process for producing a compound represented by Formula (I) ##STR00001## (wherein, R.sup.1 and R.sup.2 are each independently halogen, alkyl having 1 to 8 carbons or alkenyl having 2 to 8 carbons; m and n are each independently 0 or an integer of 1 to 4; and R.sup.3 is alkyl having 1 to 8 carbons, alkenyl having 2 to 8 carbons, cycloalkyl having 3 to 8 carbons or optionally substituted aralkyl), (1) a pH adjustment is carried out twice or more in the purification process, (2) an excessive amount of alkyl halide used is removed, (3) a solvent, such as water, containing 0.05 ppm or less of iron components is used, (4) tanks with corrosion-resistant layers over the inner walls are used, (6) a chelating agent is added, and (7) a means of drying with mechanical stir is applied.