A torsion balance is provided which includes a twisting wire and a reflector. The twisting wire is a suspended carbon nanotube. The reflector is hung on the twisting wire. The reflector further includes a film, a first reflecting layer, and a second reflecting layer; and the film includes a first surface and a second surface opposite to the first surface, and the first reflecting layer is located on the first surface and the second reflecting layer is located on the second surface.