The present invention aims to provide an electrolyte solution for forming, for example, a secondary battery having excellent oxidation resistance and high-temperature storage characteristics; an electrochemical device such as a lithium-ion secondary battery that contains the electrolyte solution; and a module that contains the electrochemical device. The present invention provides an electrolyte solution containing a solvent and an electrolyte salt, wherein the solvent contains a fluorine-containing compound (A) represented by formula (1) shown below in an amount of 0.01 to 20% by mass, and a fluorine-containing compound (B) represented by formula (2) shown below in an amount of 10 to 80% by mass: Rf1OCOOR  (1) wherein Rf1 is a C1-C4 fluorine-containing alkyl group, and R is a C1-C4 non-fluorinated alkyl group, and Rf2OCOORf3  (2) wherein Rf2 and Rf3 are the same or different, and each is a C1-C4 fluorine-containing alkyl group.