To provide an interface structure in which an interface between a solid electrolyte layer and an electrode layer is increased as compared with the conventional case.SOLUTION: There is provided an interface structure between an electrolyte layer and an electrode layer of a solid oxide fuel cell according to the present invention. In the interface structure, the electrolyte layer having oxygen ion conductivity and the electrode layer having at least one of oxygen ion and electron conductivity are bonded to each other. In an electron microscope image obtained by observing the cross section perpendicular to the surface of the electrolyte layer at magnification of 5000 times, when the length of the interface curve, which is the boundary between the electrolyte layer and the electrode layer, is set to B, and the length of a reference line which is a straight line that does not intersect the interface curve and is in contact with the interface curve at two or more points on the side of the electrolyte layer is set to A, the ratio (B/A) of the length of the interface curve to the length of the reference line is 1.2 or more and 2.7 or less.SELECTED DRAWING: Figure 2