There is disclosed a process for treating a by-product salt from a polyarylene sulfide which comprises treating a solid mixture containing an aprotic organic solvent and the by-product salt that is formed in the case of producing the polyarylene sulfide by subjecting an alkali metal sulfide and a dihalogenated aromatic compound to polymerization condensation reaction in the aprotic organic solvent, characterized in that the aprotic organic solvent is recovered by dry treating the solid mixture by the use of a dryer having a self-cleaning property. It is enabled by the above process to efficiently recover the aprotic organic solvent, and thereby produce the objective polyarylene sulfide at a lower cost.