NOVELTY - A redox flow cell consists of a charging/discharging cell (11), a primary supply pipe (13a) for supplying the positive electrode electrolyte solution (22), and a secondary supply pipe (13b) for supplying the negative electrode electrolyte solution (32). The negative electrode electrolyte solution is an electrolyte solution containing titanium redox substance and an acid (A), or an electrolyte solution containing copper redox substance and amine (I). The amount of dissolved oxygen contained in the negative electrode electrolyte solution is 1.5 mg/L or less.    USE - Redox flow cell (claimed).    ADVANTAGE - The redox flow cell has improved charge/ discharge cycle characteristics and coulomb efficiency, and is manufactured by economical process.    DETAILED DESCRIPTION - A redox flow cell consists of a charging/discharging cell, a primary tank (23) for storing positive electrode electrolyte solution, a secondary tank (33) for storing negative electrode electrolyte solution, a primary supply pipe for supplying the positive electrode electrolyte solution to the charging/discharging cell, and a secondary supply pipe for supplying the negative electrode electrolyte solution to the charging/discharging cell. The positive electrode electrolyte solution contains a ferrous redox substance and an acid (A). The negative electrode electrolyte solution is an electrolyte solution containing titanium redox substance and the acid (A), or an electrolyte solution containing copper redox substance and amine of formula (I). The acid (A) is chosen from citric acid and lactic acid. The amount of dissolved oxygen contained in the negative electrode electrolyte solution of secondary tank is 1.5 mg/L or less.    n=0-4;and    R1-R4=H, methyl, or ethyl.    DESCRIPTION OF DRAWING(S) - The drawing shows the schematic view of redox flow cell.    Charging/discharging cell (11)    Primary supply pipe (13a)    Secondary supply pipe (13b)    Positive electrode electrolyte solution (22)    Primary tank (23)    Negative electrode electrolyte solution (32)    Secondary tank (33)    Casing (41)