Abstract: In an ion generator comprising a discharge needle 2, an opposed electrode 3 opposite the discharge needle 2 and an AC high voltage power source 4, for generating positive and negative air ions by giving rise to a corona discharge when a high voltage is applied by the AC high voltage power source 4 between the discharge needle 2 and the opposed electrode 3, the AC high voltage power source 4 comprises a high frequency oscillator 7 and a piezoelectric transformer 9, and outputs a high frequency voltage. An insulator 5 is placed intervening between the high voltage output line 4a of the AC high voltage power source 4 and the discharge needle 2 to capacitance-couple them, and the discharge needle 2 is enabled to discharge electricity. Preferably, the surface of the opposed electrode 3 should be covered with an insulator. This enables the balance between positive and negative air ions and its stability to be improved while reducing the hardware configuration in size and weight.