The invention provides a charging device including a charging roll and a voltage application unit which is capable of applying to the charging roll a voltage in which an alternating current voltage is superimposed on a direct current voltage, the alternating current (Iac) which flows through the charging roll satisfying the following Equation (1), the charging roll satisfying the following conditions (a) to (c), and the charging roll contacting an image supporter to charge the image supporter: Iac/I(inflection).ltoreq.1.2 Equation (1) (in the Equation (1), I (inflection) represents the flexion point of lac) (a) the fluctuation of the outside diameter is 0.1 mm or less (b) resistance (common logarithm) is 9.0 log.OMEGA. or less (c) resistance variation (common logarithm) is 0.5 log.OMEGA. or less.