The thermoplastic resin composition of the present invention is obtained by graft polymerizing a monomer that composes a polymer that is compatible with or has affinity for polycarbonate resin in the presence of a polymer that is incompatible with polycarbonate resin; wherein, the weight average molecular weight of a soluble component that dissolves in chloroform is 10,000 to 100,000. In the case of using this thermoplastic resin composition in an engineering plastic, fluidity can be improved without impairing the characteristics of the engineering plastic. The engineering plastic composition of the present invention is preferably used in the field of housings and various parts of OA equipment, telecommunications equipment and home appliances such as photocopiers, facsimiles, televisions, radios, tape recorders, video decks, personal computers, printers, telephones, information terminals, refrigerators and microwave ovens, as well as in other fields such as automotive parts.