A redox flow battery includes a cell, an electrolyte tank configured to store an electrolyte supplied to the cell, and a circulation mechanism. The circulation mechanism includes a suction pipe configured to suck up the electrolyte from an open end thereof in the electrolyte to above an in-tank liquid level of the electrolyte in the electrolyte tank, a circulation pump, an extrusion pipe, and a return pipe. HL/H0 is greater than or equal to 0.4 and HS is less than or equal to HL, where H0 is a height from an inner bottom surface of the electrolyte tank to the in-tank liquid level, HL is a length from the open end of the suction pipe to the in-tank liquid level, and HS is a height from the in-tank liquid level to a center of a suction port of the circulation pump.