Abstract: The present invention provides a substantially linear aromatic polyester carbonate consisting essentially of hydroxybenzoic acid unit, hydroquinone unit, and carbonate unit as well as, depending on the circumstances, aromatic carboxylic acid unit, and having an inherent viscosity of at least 0.5. The present invention also provides an industrially advantageous method for producing such linear aromatic polyester carbonate through the process steps of melt-polycondensation, and, if necessary, followed by a further polycondensation in solid phase.Such aromatic polyester carbonate which the present invention provides exhibits excellent melt-forming property and melt anisotropy, hence any shaped article obtained by melt-forming of this aromatic polyester carbonate exhibits superior mechanical properties, in particular, excellent Young's modulus of longitudinal elasticity, and so on, which is highly useful as the material for industrial applications.