A binder composition that exhibits sufficient adhesion and that achieves the excellent dispersibility of a conductive additive is provided. The binder composition according to an embodiment of the present invention is a binder composition including a vinylidene fluoride copolymer composition containing vinylidene fluoride and a monomer having an acidic functional group; and a ratio (Mn2/Mn1) of a number average molecular weight of the vinylidene fluoride copolymer composition after being adsorbed onto alumina (Mn2) to a number average molecular weight of the vinylidene fluoride copolymer composition before being adsorbed onto alumina (Mn1) being less than 1.