NOVELTY - A fuel cell stack (10), comprises stack body (14) provided in box-shaped casing (24) and formed by stacking unit cells (12) in horizontal direction, where each unit cell includes electrolyte electrode assembly, and separators sandwiching electrolyte electrode assembly including pair of electrodes, and electrolyte interposed between electrodes. The separators each includes a plate and a cover covering an outer end of the plate.    USE - The fuel cell stack is used for generating electricity.    ADVANTAGE - In a fuel cell stack, a stack body formed by stacking unit cells is placed suitably in a casing, and sliding resistance between an outer region of the stack body and an inner surface of the casing is suitably reduced. The fluorocarbon resin sheets fill the gaps between the sides of the stack body and the inner surfaces of the side plates. Thus, the stack body is reliably supported without wobbling in the casing. Further, the fluorocarbon resin sheets are insulating sheets. Thus, when the unit cells contact the fluorocarbon resin sheets, no short circuit occurs between unit cells.    DETAILED DESCRIPTION - A fuel cell stack, comprises a box-shaped casing; and a stack body provided in the casing and formed by stacking unit cells in a horizontal direction, where each unit cell includes an electrolyte electrode assembly (30), and separators sandwiching the electrolyte electrode assembly including a pair of electrodes, and an electrolyte interposed between the electrodes, the separators (32, 34) each including a plate and a cover covering an outer end of the plate. The casing comprises end plates (20b) provided at opposite ends of the stack body in the stacking direction; and side plates provided on sides of the stack body. A sheet for reducing sliding resistance is provided at least between one side of the stack body and an inner surface of the side plate for filling a gap between the stack body and an inner surface of the casing.    DESCRIPTION OF DRAWING(S) - The figure is an exploded perspective view schematically showing part of a fuel cell stack.    Fuel cell stack (10)    Unit cells (12)    Stack body (14)    End plates (20b)    Box-shaped casing (24)    Electrolyte electrode assembly (30)    Separators (32, 34)