Image forming apparatus and image forming method

When printing, an image forming apparatus determines, based on a threshold voltage corresponding to a print speed during printing, whether or not a corona wire of a charger needs to be cleaned. On the basis of whether or not a monitoring voltage corresponding to a current value of a charged bias, which is applied to the corona wire by a charged-bias high-voltage power supply, is equal to or more than a predetermined threshold voltage corresponding to the print speed during printing, the image forming apparatus determines whether or not the corona wire needs to be cleaned.