An ion generating apparatus has: a housing having an intake port and an exhaust port a fan 2 having an impeller 21 and a casing 22 accommodating the impeller 21, and accommodated in the housing a filter passing the air taken in through the intake port by the fan 2 and two ion generating parts generating positive ions and negative ions. The ion generating parts are arranged in an arc-shaped guide wall 22a of the casing 22. The positive ions and the negative ions generated by the ion generating parts are efficiently mixed into air flowing in a state of laminar flow along the arc-shaped guide wall 22a.