A gas flow dividing element for a fuel cell or an electrolyzing device comprises a supporting layer (4), which is disposed with a pattern for a fluid flow and a cathode-anode-electrolyte unit (5). The cathode-anode-electrolyte unit (5) is composed of a first electrode (51), a second electrode (53) and an electrolyte (52) sandwiched between the first electrode (51) and the second electrode (53). The supporting layer (4) is arranged in a contacting relationship with the first electrode (51), whereby a reactant fluid passage (30) is formed by the pattern for fluid flow for contacting the reactant fluid with the first electrode (51). The supporting layer (4) comprises a separating element (1, 32, 34, 38) to form a gas distribution structure (33, 35, 36, 37) for dividing the reactant fluid into a first portion of reactant fluid contacting the first electrode (51) and a second portion of reactant fluid not contacting the first electrode (51).