Novel aromatic carboxylic acids and acid halides thereof, useful as raw materials for polymers, particularly heat-resistant condensation polymers; and processes for preparing the acids or the halides. The carboxylic acids and the acid halides are represented by the general formula (1) and (2) respectively: (1) (2) [wherein A is -CC-R or a group represented by the general formula (3): (3) (wherein R is hydrogen, alkyl, or an aromatic group; and R is alkyl or an aromatic group); and X is halogeno]. According to the processes of the invention, the above compounds can be efficiently prepared from dialkyl isophthalate derivatives and acetylene derivatives via specific steps.