Provided is an electrolytic solution suitable for use in a 100 WV class electrolytic capacitor having low inductance at low temperatures and high durability in high-temperature use conditions. This electrolytic solution for an electrolytic capacitor contains: a mixed organic solvent including sulfolane and γ-butyrolactone; water; an electrolyte selected from the group consisting of a quaternized pyridinium salt of carboxylic acid and a quaternized imidazolinium salt of carboxylic acid; boric acid; and mannitol; and has a mass ratio of boric acid and mannitol in the range of 1:1.2 to 1:1.6, and a total amount of boric acid and mannitol of 10.0 to 14.5% by mass of the total electrolytic solution, the water content being 1.5 to 2.0% by mass of the total electrolytic solution.