To provide a shim for preventing the squeal of a disk brake and a disk brake, which require no backup shim and are excellent in heat insulating effect.

A squeal preventing shim 1 coated with a compound layer 2 of 200-800 μ thick including a heat resisting non-metallic fiber except for asbestos and a filler, is arranged on only one side surface of a metallic plate 3, and directly opposed to pushing/pressing members 12, 14 by which brake pads 9a, 9b are push-pressed to a disk rotor 7. The compound layer 2 hardly causes permanent set even though it is thickened, therefore 'squeal' can be sufficiently prevented by arranging thickly the compound layer 2 on only the one side surface of the metallic plate 3, thus, a backup shim is no more required. A nonmetallic fiber is mixed with the compound layer 2, therefore heat resisting effect is good. If a hole or a recessed part is arranged in the shim 1, the heat resisting effect can be further improved.