In a fuel battery seal structure, a gasket has a base portion fitted in a non-bonded manner to a seal installation groove of a separator, and a seal protrusion brought into close contact with a seal groove of a separator. Presser projections and clearance grooves are formed in both sides in a width direction of the seal groove. The presser projections are brought into contact with the base portion of the gasket, and the clearance grooves are positioned in an opposite side to the seal groove as seen from the presser projections. Sum of widths of the seal groove and the presser projections in both sides thereof is smaller than a width of the seal installation groove, and sum of widths of the seal groove, and the presser projections and the clearance grooves in both sides thereof is larger than the width of the seal installation groove.