An aromatic liquid-crystalline polyester with good moldability into a film is provided. The resulting film has small dielectric loss. The polyester comprises repeating units represented by formulae (I), (II), (III) and (IV), and the molar amounts of repeating units (I)-(IV) are 40-74.8%, 12.5-30%, 12.5-30% and 0.2-15%, respectively, wherein the molecular amounts of repeating units (III) and (IV) satisfy the relation of (III)/[(III)+(IV)]0.5.