An aromatic polyether ketone of the following formula (III): ##STR13## wherein each of R1 to R12 is a hydrogen atom, a halogen atom, a hydrocarbon group or an alkoxy group, n is an integer of 0 to 5, and X is an oxygen atom, said polyether ketone being obtained by reacting, at a temperature of from -10??? to 300??? C., an aromatic ether of the formula: ##STR14## wherein each of R1 to R12 is indepe