To provide a damper, which reduces relative displacement between buildings by arrangement between the buildings as an expansion joint and can be formed in small size in the case of comparison with a conventional expansion joint.

The first plate body 8 is installed to the first steel bar 4 mounted on the exterior-wall surface 2a of the building 2 in a displaceable manner in the direction of rotation that the first steel bar 4 is used as a shaft, the second plate body 9 is secured to the second steel bar 5 set up to the exterior-wall surface 3a of the building 3 in a displaceable manner in both the direction of rotation that the second plate body 9 is used as the shaft and the direction parallel with the second steel bar 5, and the first and second plate bodies 8, 9 are bonded under a laminated state through a BRC 10 formed in a tabular shape.