disclosed herein is a wholly aromatic polyester comprising a structural unit represented by the formula : ## str1 ## a structural unit represented by the formulae , and : ## str2 ## or a structural unit represented by the formulae , and : ## str3 ## wherein x represents a c 1 to c 5 - hydrocarbon group , a halogen atom or an alkoxy group , and ## str4 ## wherein y represents an oxygen atom , a sulfur atom , a so 2 group , a carbonyl group , an alkylene group or an alkylidene group , or a single bond directly connecting the two benzene rings and r 1 , r 2 , r 3 , r 4 , r 5 , r 6 , r 7 and r 8 represent respectively a hydrogen atom , a halogen atom or a hydrocarbon group , in the case of , the aromatic polyester containing 5 to 20 mol % of the unit , 35 to 65 mol % of the unit , 15 to 45 mol % of the unit and 5 to 20 mol % of the unit , and the amount of the unit and the amount of the unit being substantially equimolar , in the case of , the aromatic polyester containing the units , , and , so that the sum of the amounts of the unit and the unit and the sum of the amounts of the unit and the unit are substantially equimolar , the ratio of the amount of the unit to the amount of the unit is from 95 : 5 to 5 : 95 and the ratio of the amount of the unit to the amount of the unit is from 65 : 35 to 100 : 0 , and the aromatic polyester showing a logarithmic viscosity of at least 0 . 4 dl / g at a concentration of 0 . 5 % by weight ).