The present invention aims to provide an electrolyte solution suitable for aluminum electrolytic capacitors which has a high spark voltage and whose conductivity does not decrease and remains sufficiently high even after heating. The electrolyte solution for aluminum electrolytic capacitors of the present invention contains a trihydric to octahydric poly alcohol alkylene oxide adduct (A), a secondary or tertiary amine, a carboxylic acid (C), and a polar solvent (D).