To provide a material composition exhibiting high vibration-damping and sound-insulating characteristics.

A first vibration-damping material composition comprises a chlorine-containing polymeric material having a chlorination degree of 30-50 wt.%, a chlorinated paraffin having an average carbon number of 20-50 and a chlorination degree of 30-50 wt.% and a chlorinated paraffin having an average carbon number of 20-50 and a chlorination degree of 50-70 wt.%. A second vibration-damping material composition comprises a chlorine-containing polymeric material having a chlorination degree of 50-70 wt.%, a chlorinated paraffin having an average carbon number of 20-50 and a chlorination degree of 30-70 wt.%, a phthalic acid-based plasticizer and a stabilizer. The vibration-damping material composition can further contain 1-20 pts.wt., based on 100 pts.wt. of the chlorine-containing polymeric material, of a rosin-based compound.