A polyphenylene sulfide resin treated by thermal oxidation has a generated gas amount of 0.23 wt % or less when the resin is heated and melted in vacuum at 320.degree. C. for 2 hours; a residual amount of 3.0 wt % or less as a residue when the resin is dissolved in an amount corresponding to 20 times the weight of the resin, of 1-chloronaphthalene at 250.degree. C. for 5 minutes and, as the 1-chloronaphthalene solution, pressure-filtered in a still hot state by a PTFE membrane filter with a pore size of 1 .mu.m or less; and a melt flow rate (measured at a temperature of 315.5.degree. C. and at a load of 5000 g according to ASTM D-1238-70) of more than 100 g/10 min to 500 g/10 min.