This invention is to provide a method of efficiently removing scales adhered to a pipe and the like. A descaled object with scales deposited thereto is covered with a solvent at least on its scaled surface. A magnetic field is generated by supply a frequency signal to a coil, and the descaled object and the solvent are disposed within this magnetic field. Signals having frequencies that are set beforehand at every scale are supplied to the coils as the frequency signals. The frequencies of the frequency signals supplied to the coils and which are set beforehand are frequencies required when an electric current flows through the solvent which covers the scales.