A monoalkylether of a dihydric phenol compound is produced at a high conversion and selectivity by catalytically dehydration reacting a dihydric phenol compound with a lower monohydric alcohol in the presence of a catalyst comprising at least one inorganic substance of the empirical formula (I):Al.sub.a P.sub.b Ti.sub.c Si.sub.d X.sub.e O.sub.f (I):wherein X is an alkali metal (Group Ia) atom, alkaline earth metal (Group IIa) atom or a metal atom of Group VIII of the Periodic Table, a, b, c, d, e and f are the numbers of Al, P, Ti, Si, X and O atoms respectively, and provided that a =1, b =1.0 to 1.9, c =0 05 to 0.5, d=0.05 to 0.2, e=0 to 0.9 and f=4.2 to 8.1, and collecting the resultant reaction product from the reaction system.