A cell stack device including: a cell stack comprising a plurality of cells; a support member; and a fixing part between the support member and the at least one cell of the plurality of cells, wherein in a cross section including the support member, the fixing part, and the at least one cell, the fixing part includes: a first region arranged close to the support member; a second region closer to the at least one cell than the first region; and a third region between the first region and the second region, and at least one of the first region and the second region includes a porous region having a porosity that is higher than a porosity of the third region.