Separators of multiple types capable of supplying and diffusing fluids such as an anode gas, cathode gas and coolant uniformly are prepared and combined to construct a fuel cell stack. Such a cell stack (20) for fuel cells includes separators of at least two types (types CA, C, A, C, CW and AW) for anode gas and cathode gas. Each separator is such that a corrosion-resistance layer is formed on at least one face of a metal plate (30) and a fluid supply and diffusion layer for the corresponding gas is formed by an electrically conductive porous layer on the corrosion-resistant layer. The at least two separators are stacked so as to face each other with at least an electrolyte membrane and catalyst layers on both sides of the membrane (a new membrane electrode assembly N-MEA) being sandwiched between the fluid supply and diffusion layers of the separators.