To provide an ion generator capable of generating positive ions and negative ions with high efficiency and in good balance, and supplying the ions far.

A voltage control part 2 of an ion generator alternately performs a first mode for applying positive high voltage Va to a positive polarity electrode 3 to generate positive ions, and a second mode for applying negative high voltage Vb to a negative polarity electrode 4 to generate negative ions. A first time Ta for performing the first mode is shorter than a second time Tb for performing the second mode. Since the positive ions diffuse faster than the negative ions, the positive ions and the negative ions are diffused in good balance.