To provide an electrode mixture capable of improving fluidity and restraining the increase of viscosity.

A positive electrode mixture contains a multivalent organic acid such as oxalic acid or a succinic acid in addition to a positive electrode active substance such as LiFePO4, a binder such as polyvinylidene fluoride, a conductive material such as carbon black and acetylene black, and a solvent such as N-methyl-2-pyrrolidone. A positive electrode mixture layer 21B is formed by coating the positive electrode mixture on a positive electrode collector 21A.