This paper presents a new type of damping material composed of flexible porous material such as polyurethane foam and liquid such as water. This new type of damping material costs less than viscoelastic materials such as Sorbothane, and is anticipated to have a better damping effect. At the same time, installation of the new type of damping material is as easy as that of usual viscoelastic materials. The damping effect of this material on the vibration of a cantilever iron plate is experimentally compared with the one of a viscoelastic material. The damping effect on a rail piece with a length of 1.2m and a weight of 72kg is also experimentally investigated. The experimental results show a good damping effect. The design variables of this new damping material such as the liquid viscosity and the hardness of the porous material are thought to influence the damping effect, consequently are investigated by carrying out vibration testing of a cantilever iron plate (material:SS400, size:300×440×5 mm , weight:5.2kg).