Abstract: To heat an object locally by automatically recognizing a shape of the object and emitting an electromagnetic wave based on the shape without enlarging a device size. An electromagnetic wave heating system comprises a heat chamber having a wall surface, in which an object is placed to be heated, a flat antenna arranged on the wall surface of the heat chamber and configured to emit the electromagnetic wave so as to heat the object inside the heat chamber, and a controller configured to control a movement of the flat antenna. The flat antenna comprises a plurality of antennas arranged in an array manner, and the controller detects a shape or a temperature distribution of the object based on a reflected power that is generated when the electromagnetic wave is emitted from the plurality of antennas, and determines a size of microwave supplied into each of the plurality of antennas based on a detection result thereof.