To provide an ion generator that causes corona discharge always in a stable state without being affected by a slight variation in the machining accuracy or assembly accuracy of a discharge electrode while further improving the generation efficiency of negative ions or positive ions compared with a conventional device.

The ion generator is provided with an electrode holder 24 made of an insulating plastic material and including a cylindrical wall 30 and a cylindrical bottom-wall 31 provided on the inner face of the cylindrical wall 30, a discharge electrode 25 arranged in a space surrounded by the cylindrical wall 30, and a counter electrode 26 arranged on the outer peripheral face of the cylindrical wall 30 so as to surround the discharge electrode 25. A discharge point P pointed into a needle shape is provided at the tip of the discharge electrode 25. A plurality of acute protrusions 38 is formed on the discharge edge face side of the counter electrode 26. By forming the acute protrusions 38, it is possible to improve the generation efficiency of negative ions or the like while causing corona discharge in a stable state.