A fuel cell system includes: a fuel cell stack (S) formed by stacking multiple unit cells (C) horizontally and having, in the stacked body, manifolds through which to supply and discharge reaction gases to and from each of the unit cells (C); and drainage paths (1A, 1B) extending from an anode-off-gas discharge manifold (M), on both end sides of the fuel cell stack (S) in the stacking direction of the unit cells, respectively.