REDOX FLOW BATTERY

The purpose of the present invention is to provide a redox flow battery in which corrosion and deterioration of a positive electrode can be suppressed and which can maintain a high charge and discharge capacity for a long period of time. The redox flow battery 1 according to the present invention is charged and discharged by circulation of an electrolyte, which contains vanadium as an active material, in a battery cell 2 including a positive electrode 10, a negative electrode 20, and a membrane 30 interposed between the electrodes 10 and 20, wherein: at least the positive electrode 10 or the negative electrode 20 contains carbon nanotubes the average diameter of which is 150 nm or smaller; and the porosity of the negative electrode 20 is higher than the porosity of the positive electrode.