A manufacturing method for a thermoplastic aromatic polyester resin composition is disclosed having a step of blending: a thermoplastic aromatic polyester resin A; an alkali composition B containing a thermoplastic aromatic polyester resin a and an alkali compound b; and a carbodiimide compound C. The alkali composition B is preferably a composition in which an aqueous solution of the alkali compound b is melt-kneaded with the thermoplastic aromatic polyester resin a. The carbodiimide compound C preferably contains an aromatic carbodiimide compound. The alkali compound U content in the thermoplastic aromatic polyester resin composition is preferably 10 ppm by mass or more and 100 ppm by mass or less.