Disclosed is an electromagnetic wave generator, comprising a tube comprising an anode, a cathode and at least one gate, a tube power supply circuit in which one side of an output terminal is connected to the anode, and the other side of the output terminal is connected to the cathode, and a gate controlling circuit in which at least one side of the output terminal is connected to the gate, wherein a first voltage value of one side of the output terminal of the tube power supply circuit and a second voltage value of the other side of the output terminal of the tube power supply circuit are different from each other with respect to a ground terminal of the tube power supply circuit.