An image forming apparatus has an image carrier with rotary shafts extending from both ends that are rotatably supported on an apparatus body by bearings. Gap members fixed to both end portions of a charging roller are brought in contact with the peripheral surface of the image carrier with some pressure to form a charge gap between the image carrier and the charging roller so that the charging roller charges the image carrier in a non-contact state with the charge gap. The gap members have a small-diameter portion on the inside thereof and a large-diameter portion on the outside thereof such that the small-diameter portions face each other.