Abstract: Heat-resistant resin composition including (A) 100 parts by weight of a poly(arylene sulfide) of a substantially linear structure containing 50% by weight or higher or recurring units of the formula ##STR1## and a logarithmic viscosity number of 0.1 to 1.0 dl/g; (B) from 0.01 to less than 25 parts by weight of a melt-stable poly(arylene thioether-ketone) having predominant recurring units of the formula ##STR2## wherein the --CO-- and --S-- are in the para position to each other, and having a melting point of 310.degree.-380.degree. C., a residual melt crystallization enthalpy of at least 10 J/g, a melt crystallization temperature of at least 210.degree. C. and a reduced viscosity of 0.2 to 2 dl/g; and (C) at least one of fibrous fibers and/or at least one of inorganic fillers in a proportion of 0 to 400 parts by weight per 100 parts by weight of the resin component including said poly(arylene sulfide) and said poly(arylene thioether-ketone).