To provide a resin composition for vibration-damping materials that is excellent in vibration damping properties, also easy to design vibration-damping materials exhibiting characteristics corresponding to applications, and useful for vibration-damping materials of various structures.

The resin composition for vibration-damping materials contains a polymer obtained by polymerizing a monomer component. The resin composition for vibration-damping materials includes at least two polymers, a polymer (A) and a polymer (B), each of which having a different weight-average molecular weight, wherein a ratio of the weight-average molecular weight of the polymer (A) to the polymer (B) is 5 or more.