A frame body that is a part of a flat cell frame for a cell stack of a redox flow battery, and that supports, on an outer peripheral side of a bipolar plate of the cell frame, the bipolar plate, the frame body including a frame-facing surface that is to face, when a plurality of the cell frames are stacked, a frame body of another cell frame that is adjacent to the cell frame in a stacking direction, wherein the frame-facing surface has a surface roughness Ra of 0.03 μm or more and 3.2 μm or less.