A process for preparing a polyarylene thioether comprising the step of oxidatively polymerizing an aromatic compound of the formula: ##STR6## where R1, R2, R3 and R4 are independently a hydrogen atom, a halogen atom, a lower alkyl group or a lower alkoxy group, and Y is a hydrogen atom or Y is a group of the formula: ##STR7## wherein R5, R6, R7 and R8 are independently a hydrogen atom, a halogen a