Ions are produced without causing any accompanying corona discharge by applying, to ion generation needles positioned so as not to contact a photoconductor drum, a voltage higher than or equal to an ion production threshold voltage and lower than a corona discharge threshold voltage. The photoconductor drum is charged by the ions produced. Accordingly, a charging device is provided which is capable of stable charging with high uniformity over a long period whilst reducing the production of ozone, nitrogen oxides, and other discharge byproducts.