PURPOSE: To provide a vibrationproof rubber without necessity of rustproofing treatment on a mechanical connected part formed out of Al die casting.

CONSTITUTION: This vibrationproof rubber is constituted of a main body rubber part 41, and a mechanical connected part 51 vulcanizedly jointed with a main body rubber part 41. It is featured that the whole or the one part of the mechanical connected part is formed out of Al alloy die casting, and the Al alloy is Al-Mg series alloy containing Mg: 3.0-5.0%, Mn: 0.2-0.6%, Si: 0.5-1.0%, Be: 0.002-0.004%, as essential components except Al.