Provided is a binder for an electrode that enables production of a slurry for an electrode that has excellent dispersibility and can cause a secondary battery to display excellent output characteristics and high-temperature cycle characteristics. The binder for an electrode contains a polymer and an organic solvent. The polymer includes a structural unit derived from a monofunctional ethylenically unsaturated carboxylic acid ester monomer in a proportion of at least 45 mass % and not more than 69.9 mass %, a structural unit derived from an aromatic vinyl monomer in a proportion of at least 30 mass % and not more than 54.9 mass %, and a structural unit derived from an ethylenically unsaturated nitrile monomer in a proportion of at least 0.1 mass % and not more than 10 mass %.