The aromatic polyester and aromatic polyester-amide of the present invention have an excellent heat resistance (soldering resistance) and are excellent in fluidity, and therefore, excellent in moldability, because they show liquid crystallinity in a molten state. In view of mechanical characteristics, the aromatic polyester and aromatic polyester-amide of the present invention have a high modulus of elasticity and are excellent in mechanical strength. In addition, the aromatic polyester and aromatic polyester-amide of the present invention have an advantage that they can be molded at a temperature of 350.degree. C. or below, especially, 320.degree. C. or below.The aromatic polyester and aromatic polyester-amide of the present invention have utility in injection molded articles, films, fibers, etc., due to the above properties thereof.In addition, the aromatic polyester and aromatic polyester-amide of the present invention become molten state at a temperature of 320.degree. C. or below, therefore, the aromatic polyester and aromatic polyester-amide can be drawn out from a reaction vessel by application of pressure or by gravity after completion of polymerization, when the polymer is produced by melt polymerization method. This is another advantage of the present invention.