PURPOSE: To perform simple and rapid drying by a method wherein a moisture content absorbed by a floor material is removed by using an electric blanket in which an electric heater is incorporated between a plurality of superposed cloths having high thermal conductivity and air permeability.

CONSTITUTION: An electric blanket 2 is formed such that an electric heater is incorporated between superposed clothes 4. The cloth 4 is a felt formed of, for example, high molecular fibers and an aluminum yarn and having 80% void and formed of a substance having high thermal conductivity and air permeability. A floor material 1 being an underfloor material is covered with the electric blanket 2. This method prevents deterioration of a floor material and maintains durability of a building.