A separator unit comprising a deformation absorbing member, an anode side separator and a cathode side separator, the deformation absorbing member stacked between the anode side separator and the cathode side separator assembled in pairs so as to absorb each deformation of stacked members of a fuel cell, the deformation absorbing member comprising: an absorbing portion for absorbing the variation of the in-plane distribution of the stress associated with deformation of the stacked members along the stacking direction, wherein the absorbing portion includes a plurality of deformable protruding portions which protrude in a grid along the stacking direction from one surface of a substrate, the substrate being in direct contact with one of the anode side separator, the cathode side separator or a plate-shaped member, wherein the plate-shaped member is in direct contact with another surface of the substrate, which faces the one surface, the plate-shaped member also being in direct contact with one of the anode side separator and the cathode side separator, wherein one protruding portion and another protruding portion are located adjacent to each other with respect to upstream side and downstream side of one circulation direction of a cooling medium to be circulated between the anode side separator and the cathode side separator, while being partly different in positions with respect to the other circulation direction crossing the one circulation direction such that the protruding portions are arranged in a staggered manner on the one surface of the substrate, wherein the protruding portion consists of a cantilevered beam portion which is erected from the one surface of the substrate, the cantilevered beam portion having a fixed end attached to the one surface of the substrate and a free end that is separated apart from the one surface of the substrate and extends along the one circulation direction from the fixed end, wherein, when deformed by being pressed by the stacking members beyond a predetermined range, the free end is brought into contact with the one of the cathode side separator, the anode side separator and the plate-shaped member. an absorbing portion for absorbing the variation of the in-plane distribution of the stress associated with deformation of the stacked members along the stacking direction, wherein the absorbing portion includes a plurality of deformable protruding portions which protrude in a grid along the stacking direction from one surface of a substrate, the substrate being in direct contact with one of the anode side separator, the cathode side separator or a plate-shaped member, wherein the plate-shaped member is in direct contact with another surface of the substrate, which faces the one surface, the plate-shaped member also being in direct contact with one of the anode side separator and the cathode side separator, wherein one protruding portion and another protruding portion are located adjacent to each other with respect to upstream side and downstream side of one circulation direction of a cooling medium to be circulated between the anode side separator and the cathode side separator, while being partly different in positions with respect to the other circulation direction crossing the one circulation direction such that the protruding portions are arranged in a staggered manner on the one surface of the substrate, wherein the protruding portion consists of a cantilevered beam portion which is erected from the one surface of the substrate, the cantilevered beam portion having a fixed end attached to the one surface of the substrate and a free end that is separated apart from the one surface of the substrate and extends along the one circulation direction from the fixed end, wherein, when deformed by being pressed by the stacking members beyond a predetermined range, the free end is brought into contact with the one of the cathode side separator, the anode side separator and the plate-shaped member.