A seal structure of a rotary machine, which has a casing and a rotating body which is rotated about an axis in the interior of said casing, said casing comprising: an outer circumference side member; and an inner circumference side member which is arranged on the inner side of said outer circumference side member in the radial direction that is orthogonal to said axis, wherein: said outer circumference side member has a ring-shaped flange which projects inward in said radial direction and which extends about the axis; said inner circumference side member is formed in a ring shape which projects outward in said radial direction and which extends about the axis, and it has a flange which is opposite to the flange of said outer circumference side member in the axial direction; on either one of the flange of said outer circumference side member and the flange of said inner circumference side member, there is formed a ring-shaped groove part which is recessed from an end surface facing the other flange side and which extends about the axis; said groove part accommodates a ring-shaped seal body which is arranged to advance and retract so as to be able to come in contact with said other flange; there are provided, at intervals in the circumferential direction, a plurality of first biasing devices which bias said seal body toward said other flange side, and a plurality of second biasing devices which bias said seal body toward a wall surface (13b,13c) of said groove part facing in said radial direction; said seal body comprises a plurality of segments arranged about the axis; a pin installation hole is formed in each of said plurality of segments and is arranged in a center part of each of said plurality of segments along the circumferential direction; and said first biasing devices and said second biasing devices are arranged alternately along the circumferential direction on both sides of the pin installation hole such that each second biasing device is located between a pair of first biasing devices. an outer circumference side member; and an inner circumference side member which is arranged on the inner side of said outer circumference side member in the radial direction that is orthogonal to said axis, wherein: said outer circumference side member has a ring-shaped flange which projects inward in said radial direction and which extends about the axis; said inner circumference side member is formed in a ring shape which projects outward in said radial direction and which extends about the axis, and it has a flange which is opposite to the flange of said outer circumference side member in the axial direction; on either one of the flange of said outer circumference side member and the flange of said inner circumference side member, there is formed a ring-shaped groove part which is recessed from an end surface facing the other flange side and which extends about the axis; said groove part accommodates a ring-shaped seal body which is arranged to advance and retract so as to be able to come in contact with said other flange; there are provided, at intervals in the circumferential direction, a plurality of first biasing devices which bias said seal body toward said other flange side, and a plurality of second biasing devices which bias said seal body toward a wall surface (13b,13c) of said groove part facing in said radial direction; said seal body comprises a plurality of segments arranged about the axis; a pin installation hole is formed in each of said plurality of segments and is arranged in a center part of each of said plurality of segments along the circumferential direction; and said first biasing devices and said second biasing devices are arranged alternately along the circumferential direction on both sides of the pin installation hole such that each second biasing device is located between a pair of first biasing devices. said outer circumference side member has a ring-shaped flange which projects inward in said radial direction and which extends about the axis; said inner circumference side member is formed in a ring shape which projects outward in said radial direction and which extends about the axis, and it has a flange which is opposite to the flange of said outer circumference side member in the axial direction; on either one of the flange of said outer circumference side member and the flange of said inner circumference side member, there is formed a ring-shaped groove part which is recessed from an end surface facing the other flange side and which extends about the axis; said groove part accommodates a ring-shaped seal body which is arranged to advance and retract so as to be able to come in contact with said other flange; there are provided, at intervals in the circumferential direction, a plurality of first biasing devices which bias said seal body toward said other flange side, and a plurality of second biasing devices which bias said seal body toward a wall surface (13b,13c) of said groove part facing in said radial direction; said seal body comprises a plurality of segments arranged about the axis; a pin installation hole is formed in each of said plurality of segments and is arranged in a center part of each of said plurality of segments along the circumferential direction; and said first biasing devices and said second biasing devices are arranged alternately along the circumferential direction on both sides of the pin installation hole such that each second biasing device is located between a pair of first biasing devices.