To provide an inexpensive friction damper applicable to a low-strength structure such as an old existing building.

The friction damper is mounted between two members to be relatively moved for damping vibration between the two members. It includes a motion converting mechanism for converting reciprocative linear moving motion relating to the relative movement into reciprocative rotating motion with a predetermined axial center as a rotating center, a rotary inertia mass rotatably supported on one of the two members around the axial center and adapted to be rotated with the rotating motion, a friction material provided on the rotary inertia mass and adapted to be rotated integrally with the rotary inertia mass, and a sliding material provided on one member for damping vibration with friction force generated between the friction material and itself by sliding motion against the friction material. The motion converting mechanism sets the rotating speed of the friction material around the axial center to be faster than the speed of the linear moving motion.

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