A stack structure of fuel cells, wherein a plurality of fuel cells which include an electrolyte layer, and an air electrode layer and a fuel electrode layer on both surfaces of the electrolyte layer are stacked in the stack structure, the stack structure comprising: an interconnector disposed between a first and second fuel cells, which are adjacent to each other, of the plurality of fuel cells and electrically connected to the air electrode layer of the first fuel cell and the fuel electrode layer of the second fuel cell, the interconnector formed of a conductive material comprising first partition walls disposed on an upper surface of the interconnector to form a plurality of first channels on the upper surface and second partition walls disposed on a lower surface of the interconnector to form a plurality of second channels on the lower surface; and a current collector disposed between the air electrode layer of the first fuel cell and the interconnector for electrically connecting the air electrode layer of the first fuel cell with the interconnector, wherein the current collector includes a metal thin plate, through which a plurality of openings pass through such that the air directly contacts with the air electrode layer of the first fuel cell, having an upper even surface surface-contacting with the air electrode layer of the first fuel cell and a lower even surface surface-contacting with the first partition walls, wherein the openings are positioned at only corresponding positions at which the first channels of the interconnector are formed, wherein the upper and lower surfaces of the metal thin plate except for the openings are flat, and wherein the current collector surface-contacts with the air electrode layer of the first fuel cell and the first partition walls to disperse a load of the stack structure in which the plurality of the fuel cells are stacked, characterized in that the openings are uniformly formed in different shapes or sizes in each area and the openings are formed to be increased in sizes in every predetermined area along a direction D in which the air flows and the openings disposed adjacent to an area in which the air is supplied into the first channels have a size smaller than that of the openings disposed adjacent to an area in which the air is exhausted from the first channels. an interconnector disposed between a first and second fuel cells, which are adjacent to each other, of the plurality of fuel cells and electrically connected to the air electrode layer of the first fuel cell and the fuel electrode layer of the second fuel cell, the interconnector formed of a conductive material comprising first partition walls disposed on an upper surface of the interconnector to form a plurality of first channels on the upper surface and second partition walls disposed on a lower surface of the interconnector to form a plurality of second channels on the lower surface; and a current collector disposed between the air electrode layer of the first fuel cell and the interconnector for electrically connecting the air electrode layer of the first fuel cell with the interconnector, wherein the current collector includes a metal thin plate, through which a plurality of openings pass through such that the air directly contacts with the air electrode layer of the first fuel cell, having an upper even surface surface-contacting with the air electrode layer of the first fuel cell and a lower even surface surface-contacting with the first partition walls, wherein the openings are positioned at only corresponding positions at which the first channels of the interconnector are formed, wherein the upper and lower surfaces of the metal thin plate except for the openings are flat, and wherein the current collector surface-contacts with the air electrode layer of the first fuel cell and the first partition walls to disperse a load of the stack structure in which the plurality of the fuel cells are stacked, characterized in that the openings are uniformly formed in different shapes or sizes in each area and the openings are formed to be increased in sizes in every predetermined area along a direction D in which the air flows and the openings disposed adjacent to an area in which the air is supplied into the first channels have a size smaller than that of the openings disposed adjacent to an area in which the air is exhausted from the first channels.