To easily renew an existing sound-insulating floor to a sound-insulating floor with a good feeling of walking by replacing an existing sound-insulating flooring material with a new sound-insulating flooring material, for example, when the sound-insulating flooring material is partially damaged, in the case of the existing sound-insulating floor in which the sound-insulating flooring materials adjacent to each other are connected together via a tongue and a groove, undergoing tongue-and-groove jointing.

After the existing sound-insulating flooring material 1 to be renewed is removed from on a sub-floor, an elastic supporting piece 8, which is composed of a cushion material more rigid than a cushion material 4 stuck on the undersurface of the existing sound-insulating flooring material, is arranged below the tongue 6 of either of the existing sound-insulating flooring materials 1 and 1 adjoining each other via a trace after the removal of the existing sound-insulating flooring material 1. After a downside protrusive streak portion 5b of the groove 5 of the new sound-insulating flooring material 1' is cut off, an upside protrusive streak portion 5a of the groove 5 of the new sound-insulating flooring material 1' is received on the tongue 6 of the existing sound-insulating flooring material 1 which is supported by the elastic supporting piece 8, and the tongue 6 is fitted into the groove 5 of the other existing sound-insulating flooring material 1.