This invention provides a cell frame for a redox flow battery that prevents leakage of electrolyte out of the cell frame and also provides a good workability in assembling the redox flow battery. Also, this invention provides a redox flow battery using the cell frame. In the cell frame 30 for the redox flow battery 30 comprising a bipolar plate 21 and a frame 31 fitted around a periphery of the bipolar plate 21, the frame 31 has, on each side thereof, an inner seal and an outer seal to press-contact with a membrane and also seal electrolyte. The frame 31 has, on each side thereof, an inner seal groove 34 and an outer seal groove 35 for placing therein the inner seal and the outer seal, respectively, to prevent the electrolyte from leaking out, and O-rings are placed in the respective seal grooves.