To obtain a modified polyarylene sulfide which, when compounded with a thermoplastic resin, can give a resin compsn. having very high mechanical strengths such as impact and tensile strengths by compounding a polyarylene sulfide with a specific compd.

A hurdred (100) pts.wt. polyarylene sulfide having a methylene chloride extractable content of 0.7wt.% or lower, a melt viscosity V6 of 20-15,000P, and a content of SX groups (wherein X is H or an alkali metal) of 15μmol or higher is compounded with 0.01-20 pts.wt. compd. represented by the formula (wherein Ar is a 6-20C mono-to tetravalent arom. hydrocarbon group having at least one glycidyloxy group bonded to the arom. ring; R is H or methyl; and (n) is 1-4). Thus, giving a modified polyarylene sulfide, which is highly compatible with a thermoplastic resin and is compounded with a thermoplastic resin in an amt. of 10-900wt.% of the modified polyarylene sulfide.