An ion generator that can generate a controlled trace amount of ozone together with negative or positive ions. The ion generator includes an insulation substrate, a ground electrode and a high-voltage electrode on the insulation substrate, an insulating film formed on the ground electrode, and a wire electrode. The root of the wire electrode is soldered to the high-voltage electrode. The tip of the wire electrode is arranged so as to protrude in a recessed part. The ground electrode has a pair of legs disposed on the insulation substrate at the sides of the recessed part. The legs are parallel to the wire electrode on opposite sides of the wire electrode. The insulating film is provided on the surface of the ground electrode to cover the ground electrode except the high-voltage electrode contacting a first terminal, a contact portion contacting a second terminal and parts of the legs of tips of the ground electrode that face the tip of the wire electrode.