A neutralizer 1 includes: a power supply circuit 11; an output controlling circuit 12 configured to convert a DC voltage generated by the power supply circuit 11 to a high-frequency voltage with frequency equal to or higher than an audible frequency, and thus to output the resultant high-frequency voltage alternately to two output lines at regular intervals; a transforming circuit 13 configured to raise the high-frequency voltage; a discharger 20 including 2n (n is an integer equal to one or more) discharge needles configured to output positive ions in response to application of a positive polarity voltage, and to output negative ions in response to application of a negative polarity voltage, the discharge needles being disposed while being divided into first and second groups each including n discharge needles; a polarity reversing circuit 14 configured to convert the high-frequency high voltage outputted from the transforming circuit 13, to two rectangular-wave DC high voltages with different polarities during a certain period, and to output the two DC high voltages respectively to the first and second groups in the discharger 20 while reversing the polarities of the two DC high voltages at regular intervals; and an air blower configured to blow air from a windward side of the discharger 20.