Provided is a binder for electricity storage devices, the binder being one with which favorable adhesiveness is obtained and which is capable of favorably limiting swelling due to electrolyte solutions. A binder for electricity storage devices that is obtained from a fluorine-containing copolymer comprising structural units (A), structural units (B), and structural units (C) and the mole ratio of structural units (C) with respect to the total of all structural units excluding the structural units (C) is 0.01/100 to 3/100. The structural unit (A) is a structural unit originating from a monomer selected from a group comprising tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride, and chlorotrifluoroethylene. The structural unit (B) is a structural unit originating from ethylene or propylene. The structural unit (C) is a structural unit originating from a C5 to C30 organic compound that has two or more double bonds, and at least one of the double bonds is the double bond of a vinyl ether group or the double bond of a vinyl ester group.