A process for preparing a polyarylene thioether, comprising oxidation polymerizing at least one compound selected from the group consisting of diaryl disulfides represented by the formula (I): ##STR1## wherein, S is a sulfur atom, R.sup.1 to R.sup.8 are identical or different and each is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a halogen atom or an alkoxyl group having 1 to 10 carbon atoms, with at least one catalyst selected from the group consisting of vanadyl acetylacetonato, vanadyltetraphenyl porphyrin, vanadium acetylacetonato, vanadyl porphyrin, vanadium porphyrin, oxymolybdenum acetylacetonato and oxytungsten acetylacetonato, in the presence of an acid. Reaction conditions of the process are very mild, and the process is relatively simple and easy. In addition, the process is commercially advantageous in that very inexpensive reactants and catalysts can be used.