A seal device inserted into and disposed between grooves each formed at each of first and second components (50A, 50B) which are adjacent to each other and collectively form a housing structure of power equipment such as gas turbines and gas turbine engines, the seal device being configured to seal a clearance between the first component and the second component (50A, 50B), comprising: a first seal member (2A, 102A, 202A, 302A, 402A) inserted into the groove of the first component; a second seal member (2B, 102B, 202B, 302B 402B) inserted into the groove of the second component; and a partitioning member (3, 103, 203, 303, 403) extending between the first and second seal members (2A, 2B, 102A, 202A, 302A,402B, 102B, 202B, 302B,402B) to partition a space between the grooves of the first and second components (50A, 50B) and arranged movably relative to the first and second seal members (2A, 2B, 102A, 202A, 302A, 402A, 102B, 202B, 302B, 402B), characterized in that the partitioning member (3, 103, 203, 303, 403) includes a base portion (30a, 230a) formed in a flat plate shape and projecting portions (30b, 30c, 130c) formed at both ends of the base portion (30a, 230a) in a transverse direction thereof and extending in a longitudinal direction of the partitioning member (3, 103, 203, 303, 403) and having a greater thickness than that of the base portion (30a, 230a), and each of the first and second seal members (2A, 2B, 102A, 202A, 302A,402A, 102B, 202B, 302B, 402B) is provided with a hollow in which the projecting portions (30b, 30c, 130c) are housed and a slit-shaped opening which is formed with a shorter dimension in a thickness direction than a dimension of each projecting portion (30b, 30c, 130c) in the thickness direction and into which the base portion (30a, 230a) is inserted, wherein the projecting portions (30b, 30c, 130c) are formed in such a manner that both end portions of the partitioning member (3, 103, 203, 303, 403) in a transverse direction thereof are folded back, wherein each of the projecting portions (30b, 30c, 130c) is divided into multiple projecting elements scattered in the longitudinal direction, wherein the projecting elements are sorted into a first group in which the projecting elements are formed by folding back the end portions of the partitioning member (3, 103, 203, 303, 403) to a front side of the base portion (30a, 230a) and a second group in which the projecting elements are formed by folding back the end portions of the partitioning member (3, 103, 203, 303, 403) to a back side of the base portion (30a, 230a). a first seal member (2A, 102A, 202A, 302A, 402A) inserted into the groove of the first component; a second seal member (2B, 102B, 202B, 302B 402B) inserted into the groove of the second component; and a partitioning member (3, 103, 203, 303, 403) extending between the first and second seal members (2A, 2B, 102A, 202A, 302A,402B, 102B, 202B, 302B,402B) to partition a space between the grooves of the first and second components (50A, 50B) and arranged movably relative to the first and second seal members (2A, 2B, 102A, 202A, 302A, 402A, 102B, 202B, 302B, 402B), characterized in that the partitioning member (3, 103, 203, 303, 403) includes a base portion (30a, 230a) formed in a flat plate shape and projecting portions (30b, 30c, 130c) formed at both ends of the base portion (30a, 230a) in a transverse direction thereof and extending in a longitudinal direction of the partitioning member (3, 103, 203, 303, 403) and having a greater thickness than that of the base portion (30a, 230a), and each of the first and second seal members (2A, 2B, 102A, 202A, 302A,402A, 102B, 202B, 302B, 402B) is provided with a hollow in which the projecting portions (30b, 30c, 130c) are housed and a slit-shaped opening which is formed with a shorter dimension in a thickness direction than a dimension of each projecting portion (30b, 30c, 130c) in the thickness direction and into which the base portion (30a, 230a) is inserted, wherein the projecting portions (30b, 30c, 130c) are formed in such a manner that both end portions of the partitioning member (3, 103, 203, 303, 403) in a transverse direction thereof are folded back, wherein each of the projecting portions (30b, 30c, 130c) is divided into multiple projecting elements scattered in the longitudinal direction, wherein the projecting elements are sorted into a first group in which the projecting elements are formed by folding back the end portions of the partitioning member (3, 103, 203, 303, 403) to a front side of the base portion (30a, 230a) and a second group in which the projecting elements are formed by folding back the end portions of the partitioning member (3, 103, 203, 303, 403) to a back side of the base portion (30a, 230a).