To provide a variation control structure for further effectively extracting the damping force of a damper, and restraining the out-of-plane deformation of a brace and the damper.

This variation control structure is constituted by installing the damper 28 between nodal points 30 and 31 being a diagonal point of the other set of a quadrangle by respectively rotatably pin-joining a set of diagonal points of the quadrangle formed by rotatably pin-joining brace members 21 and 21 to an upper fulcrum 16 and a lower fulcrum 17 arranged above and below a column-beam frame surface 40, and installing expandable arms 27L and 27R between the nodal points 30 and 31 and fulcrums 23 and 24 arranged on the column member side. The arms 27L and 27R are also formed as crank-shaped arms of pin-joining arm members 25 and 25.