PURPOSE: To provide a method of manufacturing a work heating apparatus and motor which can heat a work in a short time and improve reliability and productivity by preventing damage of a work such as rotor of a motor.

CONSTITUTION: An annular iron core 10 having, at a part thereof, a gap portion 11 to which a work (rotor) 1 is removably inserted, an energizing coil 12 to be loaded to this annular iron core and a high frequency variable power supply 13 to be electrically connected with this energizing coil to apply a power to this energizing coil are comprised. Thereby, an AC field is applied to the annular iron core to generate an eddy current and the rotor is uniformly and quickly heated with an iron loss thereof.