PURPOSE: To prolong the service life of catalytic activity by using partially- substituted calcium hydroxylapatite which is substituted with specified alkaline earth metal and if necessary, incorporating oxide of a specified element therein and molding the titled catalyst.

CONSTITUTION: A catalyst for a vapor-phase intermolecular dehydrating reaction of alkanolamines is molded by using partially-substituted calcium hydroxylapatite which is obtained by substituting calcium hydroxylapatite and one part of calcium element incorporated therein with alkali metallic elements and/or alkaline earth metallic elements excepting calcium. If necessary, oxide of at least one kind of element selected from a group consisting of Mg, Sr, Ba, B, Si, P, Ti, Zr, Nb, Mo, Ta, W, Bi and Co is contained in this catalyst.