A fixing device includes a fixing member, a pressing member, a charger, and adjusting part. The fixing member heats toner images on media. The pressing member forms nips with the fixing member and presses the media. The charger uses a corona discharge that occurs in an electric field generated around a discharging electrode so as to charge the fixing member to a same polarity of toner in the toner images. The adjusting part increases a bias applied to the discharging electrode in accordance with increase of a cumulative number calculated by accumulating a number of the media on which the toner images are fixed or increase of a cumulative printing amount calculated by multiplying a printing rate that indicates a ratio of an area of the toner images to an area of the media by the cumulative number.