A liquid-crystalline polyester for film having small linear expansibility and high flexibility is provided. The polyester may have structural units --O--Ar1-CO--, --NH--Ar2-X--, --CO--Ar3-CO-- and --CO--Ar4-Z-Ar5-CO-- wherein Ar1 represents 1,4-phenylene, 2,6-naphthylene or 4,4'-biphenylene, Ar2 represents 1,4-phenylene or 1,3-phenylene, X represents --O-- or --NH--, Ar3 represents 1,4-phenylene, 1,3-phenylene or 2,6-naphthylene, Ar4 and Ar5 independently represent 1,4-phenylene, 2,6-naphthylene or 4,4'-biphenylene, and Z represents --O--, --SO.sub.2-- or --CO--, in which the amount of monomer (1) is 30-80% by mol, the amount of monomer (2) is 10-35% by mol, the total amount of monomers (3) and (4) is 10-35% by mol and the amount of monomer (4) is 1% by mol or larger.