The present invention relates to a corona charging apparatus for charging a body to be charged that has a discharge wire electrode to which a voltage is applied, a shield electrode having an opening opposed to the body to be charged, a grid electrode disposed in the opening, a power supply for applying a voltage to the grid electrode, and a constant voltage generating element electrically connected to the grid electrode, the constant voltage generating element generating predetermined voltage when current flows into the constant voltage generating element, and rated voltage of the constant voltage generating element is equal to or greater than the voltage applied to the grid electrode from the power supply.