Disclosed herein is a flat-tubular solid oxide cell stack. The cell stack includes a plurality of unit cells which are stacked one on top of another. Each unit cell includes a flat-tubular electrode support made of a porous conductive material. A first-gas flow channel is formed in the electrode support in a longitudinal direction thereof. First gas flows along the first-gas flow channel. A second-gas flow channel is formed on the outer surface of the electrode support. Second-gas flows along the second-gas flow channel. A connection hole is formed on each of opposite ends of the first-gas flow channel of each of the unit cells and communicates with the first-gas flow channel of the adjacent unit cell so that the first gas flows along the unit cells in a zigzag manner in the longitudinal directions of the unit cells.