To provide an electrolytic solution for electrolytic capacitor, having superior high-temperature service life characteristics and high flame retardance.

This electrolytic solution is prepared, by adding at least one or more kinds of organic carboxylic acid compounds selected from among 1,6-decane-dicarboxylic acid, etc., or their salts in an amount of 1-15 wt.% and an ester monoalkylphosphate compound to an electrolytic solution, obtained by dissolving a polyhydric alcohol complex compound of boric acid obtained from boric acid and polyhydric alcohol or its salt in a solvent, composed mainly of ethylene glycol in an amount of 10-30 wt.% and adjusting the water content to 9-30 wt.%. Accordingly, when this electrolytic solution is used in an electrolytic capacitor, the high-temperature service life characteristic and flame retardance of the capacitor are improved.