Abstract: An upper board fixed to a lower part of a structure; a lower board fixed to a foundation at the same position in a plan view with respect to the upper board; and four seismic isolation plates fixed to the upper and lower boards and extending in a cross direction in a plan view. The seismic isolation plates are U-shaped members obtained by bending a long steel sheet, and include an upper fixing part parallel to a lower fixing part, an upper inclined part and a lower inclined part that are closer to each other while separated from the upper and lower fixing parts, and a connecting part that connects the upper and lower inclined parts. The four seismic isolation plates are fixed to upper board at position where upper fixing parts do not overlap and are fixed to lower board at position where lower fixing parts do not overlap.

Abstract: A brace member includes a plastically deformable core member, a buckling restraining member through which the core member extends, a cap sleeve in which a first end portion of the core member and a first end portion of the buckling restraining member are disposed, a cap-sleeve crevice disposed on the cap sleeve so as to protrude toward a side opposite to a side on which the core member and the buckling restraining member are disposed, a reinforcing member in which a second end portion of the core member is disposed, and a reinforcing-member crevice disposed on the reinforcing member so as to protrude toward a side opposite to a side on which the core member is disposed. The reinforcing member surrounds a predetermined area of the buckling restraining member extending from a second end surface on the second side in the longitudinal direction.