A separator assembly for a fuel cell applied to a fuel cell stack configured by single cells laminated in a laminating direction, each of the single cells including a membrane electrode assembly, a first separator having a base made of a metal plate and arranged on an anode side of the membrane electrode assembly, and a second separator having a base made of a metal plate and arranged on a cathode side of the membrane electrode assembly, the separator assembly comprising: the first separator; the second separator, wherein the first separator and the second separator are adjacent to each other in the laminating direction; and a joined portion where the first separator and the second separator are joined to each other through laser welding, wherein the first separator includes first projections and first recesses, both of which extend, the first projections and the first recesses being alternately arranged, the second separator includes second projections and second recesses, both of which extend, the second projections and the second recesses being alternately arranged, the first separator includes a first surface and a back surface located on the opposite side from the first surface, the first surface being intended to be opposed to the membrane electrode assembly, a film, which includes conductive particles, is arranged on a part of the first surface of the first separator corresponding to a top surface of each first projection, wherein the part of the first surface corresponding to the top surface of each first projection is configured to abut the membrane electrode assembly, and a portion of the first surface other than the part corresponding to the top surface of each first projection is an exposed portion where the film is not arranged and the base of the first separator is exposed, the second separator includes a second surface and a back surface located on the opposite side from the second surface, the second surface being intended to be opposed to the membrane electrode assembly, a film including conductive particles is arranged on the entire second surface of the second separator, the first separator and the second separator are arranged such that parts of the back surface of the first separator corresponding to bottoms of the first recesses and parts of the back surface of the second separator corresponding to bottoms of the second recesses are abutted against each other, and the joined portion is formed by irradiating a part of the exposed portion of the first surface of the first separator corresponding to the bottom of each first recess with laser. the first separator; the second separator, wherein the first separator and the second separator are adjacent to each other in the laminating direction; and a joined portion where the first separator and the second separator are joined to each other through laser welding, wherein the first separator includes first projections and first recesses, both of which extend, the first projections and the first recesses being alternately arranged, the second separator includes second projections and second recesses, both of which extend, the second projections and the second recesses being alternately arranged, the first separator includes a first surface and a back surface located on the opposite side from the first surface, the first surface being intended to be opposed to the membrane electrode assembly, a film, which includes conductive particles, is arranged on a part of the first surface of the first separator corresponding to a top surface of each first projection, wherein the part of the first surface corresponding to the top surface of each first projection is configured to abut the membrane electrode assembly, and a portion of the first surface other than the part corresponding to the top surface of each first projection is an exposed portion where the film is not arranged and the base of the first separator is exposed, the part of the first surface corresponding to the top surface of each first projection is configured to abut the membrane electrode assembly, and a portion of the first surface other than the part corresponding to the top surface of each first projection is an exposed portion where the film is not arranged and the base of the first separator is exposed, the second separator includes a second surface and a back surface located on the opposite side from the second surface, the second surface being intended to be opposed to the membrane electrode assembly, a film including conductive particles is arranged on the entire second surface of the second separator, the first separator and the second separator are arranged such that parts of the back surface of the first separator corresponding to bottoms of the first recesses and parts of the back surface of the second separator corresponding to bottoms of the second recesses are abutted against each other, and the joined portion is formed by irradiating a part of the exposed portion of the first surface of the first separator corresponding to the bottom of each first recess with laser.