The present invention relates to a modular redox flow battery comprising a positive electrolyte tank, a negative electrolyte tank, a positive electrolyte, a negative electrolyte, a plurality of stacks, pipes, a positive electrolyte pump and a negative electrolyte pump, a battery management system (=BMS), and sensors, wherein the stacks and the BMS 500 are mounted on a stack frame 800, the positive electrolyte tank and the negative electrolyte tank are mounted on a tank frame 900, and the stack frame 800 and the tank frame 900 are combined.