An electrolyte solution capable of providing electrochemical devices whose internal resistance is less likely to increase even after repeated charge and discharge and whose cycle capacity retention ratio is high. The electrolyte solution contains a solvent, an electrolyte salt, and a phosphate in an amount of 0.001 to 15 mass % relative to the solvent and represented by the formula (1): (R11O)(R12O)PO2M, where R11, R12 and M are as defined herein.