Supercoil Company Ltd. has commercialized a 300-k W-high-Tc-based superconducting induction heater (SIH). Supercoil has many patents related to the SIH as well as technologies to maintain thermal stability and reliability in the operation of a high-Tc superconducting magnet against uneven quench through the metal insulation winding method. Here, two high-temperature superconducting (HTS) magnets were installed with the two iron cores. The configuration of the 300-kW SIH was introduced. The heating simulation results of the various metal billets were shown through the temperature distribution of the billet. Operating results of the HTS magnets, such as the terminal voltages, excitation current, magnetic flux density, and magnet temperature, are presented and shown. Through these results, metal industries gain access to SIH reference information.