A damper in which magnetic particles are difficult to sediment irrespective of the kind of a magnetic fluid is provided. A damper is constituted of a vessel in which the magnetic fluid is accommodated and a slider (piston). As the piston, one that is made of a laminated body of a paramagnetic substance and a non-magnetic substance is used. When thus constituted, the magnetic particles stick to the piston. Accordingly, whatever magnetic fluid is used, the particles do not sediment. The laminated body that is used as the piston has the non-magnetic substance at both ends thereof. When the laminated body is thus constituted, the magnetic particles sticks uniformly. When the laminated body has the magnetic substance at both ends, magnetic particles stick to both ends needle-like.