MEMBRANE FOR REDOX FLOW BATTERY, METHOD FOR PRODUCING MEMBRANE FOR REDOX FLOW BATTERY, MEMBRANE ELECTRODE ASSEMBLY FOR REDOX FLOW BATTERY, CELL FOR REDOX FLOW BATTERY, AND REDOX FLOW BATTERY

An object of the present invention is to provide a membrane for a redox flow battery which is prevented from being curled and exhibits high power efficiency, a membrane electrode assembly for a redox flow battery, a cell for a redox flow battery, and a redox flow battery. The object can be attained by a membrane for a redox flow battery, comprising a first ion-exchange resin layer, an anion-exchange resin layer containing an anion-exchange compound, and a second ion-exchange resin layer in the presented order, wherein a value obtained by dividing a thickness of the first ion-exchange resin layer by a thickness of the second ion-exchange resin layer is 0.7 or more and 1.3 or less, and a thickness of the anion-exchange resin layer is 0.02 μm or larger and 3 μm or smaller.