A redox flow battery 1 including: a battery cell (10) including a positive electrode (11), a negative electrode (12), and an ion exchange membrane (13); a positive electrode-side electrolyte tank (20); a negative electrode-side electrolyte tank (30); a positive electrode-side pipe connecting the battery cell (10) to the positive electrode-side electrolyte tank (20); and a negative electrode-side pipe connecting the battery cell (10) to the negative electrode-side electrolyte tank (30). The redox flow battery (1) performs charge and discharge by circulating respective electrolytes between the battery cell (10) and the positive electrode-side electrolyte tank (20) through the positive electrode-side pipe (21, 22) and between the battery cell (10) and the negative electrode-side electrolyte tank (30) through the negative electrode-side pipe (31, 32). A hydrogen gas amount decreasing means (40) having a hydrogen gas amount decreasing device (60) is provided on the negative electrode-side pipe (31, 32).