The cooling device of the present invention is intercalated to the fuel cells assembled in a stack and comprises a planar, elastically deformable, conductive and porous element capable of ensuring both the passage of a suitable coolant and the electrical continuity between the walls delimiting the same. The planar conductive deformable and porous element is characterized by being provided with linear sections capable of guiding the coolant flow so as to reliably achieve a uniform heat withdrawal. The linear sections may have a straight shape and consist of inert impervious and preferably elastic material.