High-quality polyarylene-thioether fibers are provided, which simultaneously satisfy the following conditions:(a) the polyarylene-thioether is a linear polyarylene-thioether having a melt viscosity of 5,300 to 20,000 poise (at 310.degree. C. and a shear velocity of 200 second.sup.-1);(b) the fiber diameter is in the range of 1 to 50 microns;(c) the tensile strength is not less than 40 kg/sq.mm;(d) the tensile modulus of elasticity is not less than 500 kg/sq.mm; and(e) the tensile strength at 200.degree. C. is not less than 20 kg/sq.mm.The fibers are produced by continuously melt-spinning a linear polyarylene-thioether polymer having a melt viscosity of 5,300 to 20,000 poise (at 310.degree. C. and a shear velocity of 200 second.sup.-1), continuously stretching the spun filament, and continuously heat-setting the stretched filament for 0.02 to 100 seconds at a temperature of not lower than the melting point of the polymer minus 100.degree. C.