Abstract: A solid oxide fuel cell and method of making same is disclosed. An electrolyte layer of an oxide ion conductor material that may be specified by La1−aAaGa1−(b+c)BbCocO3 and an air electrode layer of an electron conductor material that may be specified by La1−dAdCoO3 are laminated, preferably with an intermediate layer of an electron and ion mixed conductor material that may be specified by La1−eAeGa1−(f+g)BfCogO3 interposed therebetween. The laminate may be sintered to integrate the layers, and may then subjected to a heat treatment to cause elements to diffuse through an interface between adjoining layers. The composition in each interface is thus continuously changed. Here, A may be at least one element selected from the group consisting of Sr and Ca, B may be at least one element selected from the group consisting of Mg, Al, and In, and 0.05≦a≦0.3, 0≦b, e≦0.3, 0≦c≦0.15, b+c≦0.3, 0≦d≦0.5, 0≦f≦0.15, 0.15<g≦0.