Provided are a binder composition which has high electrolyte resistance characteristics, and a secondary battery which uses a positive electrode using the binder composition for high-temperature cycle characteristics. [Solution] The binder composition for the secondary battery positive electrode according to the present invention contains a polymerized unit which contains a nitrile group; a polymerized unit of (meth) acrylic acid ester; a polymerized unit which contains a hydrophilic group; and a polymerized unit of linear alkylene having a carbon number of at least four. In a mixed solvent in which a volume ratio EC:DEC between ethylene carbonate (EC) and diethyl carbonate (DEC) at 20° C. is 1:2, a degree of swelling with respect to an electrolyte in which LiPF6 is dissolved to have a concentration of 1.0 mol/L is between 100% and 500%.