A charging device includes a charging member that charges a body to be charged; a detector that detects an AC component of a current flowing through the charging member; an integration section that integrates the AC component of the current detected by the detector; a controller that controls the current flowing through the charging member, according to a result of integration executed by the integration section; a periodic signal generating section that generates a periodic signal having a cycle period corresponding to a cycle period of the AC component; and an integration period adjusting section that adjusts a period of integration executed by the integration section, with reference to the periodic signal.