A fluid passage structure for a fuel cell stack according to this invention comprises an internal manifold (16) formed on an inner side of a laminated body (1) of a plurality of fuel cells in a lamination direction, an external fluid passage (22) that supplies a fluid to the internal manifold (16), and a connection portion (16a) that connects the fluid passage to the internal manifold. Each fuel cell comprises an in-cell fluid passage (15) that is connected to the internal manifold (16) from an orthogonal direction. By forming the connection portion (16a) such that a swirl is generated in the internal manifold (16) using the energy of the fluid that flows into the internal manifold (16) from the fluid passage (22), a pressure deviation in a transverse section of the internal manifold (16) is reduced, and the fluid supply rate to each in-cell fluid passage (15) is made even.