An electromagnetic heating device for heating a target object by irradiating electromagnetic wave includes a chamber configured to accommodate the target object, an electromagnetic wave irradiation unit configured to irradiate the electromagnetic wave to the target object in the chamber, wherein an oscillation frequency of the irradiated electromagnetic wave is variable, and a control unit configured to control heating by the electromagnetic wave. The control unit draws, on a complex plane, complex relative permittivity characteristics indicating change in a complex relative permittivity of the target object when a frequency of the irradiated electromagnetic wave varies, also draws a non-reflection curve on the complex plane, determines a frequency of the electromagnetic wave and a thickness of the target object based on a value derived from an intersection point between the complex relative permittivity characteristics and the non-reflection curve, and performs electromagnetic heating based on the determined frequency and thickness.