An image forming apparatus, includes: a developer moving element that moves developer in order to transfer the developer onto a medium by rotating with the developer being borne on the developer moving element; and a collector for collecting the developer that has not been transferred onto the medium and remains on the developer moving element, the collector having a scraper blade that can abut against and separate from the developer moving element and that is for scraping off the developer on the developer moving element by abutting against the developer moving element, a sealing member that can contact with and separate from the developer moving element and that is for preventing, by contacting the developer moving element, the developer from spilling outside the collector, a ventilation opening for moving air in the collector outside the collector, and a valve for adjusting an amount of air passing through the ventilation opening, and the collector being made such that when either one of the scraper blade and the sealing member, whichever separates earlier from the developer moving element, starts separating therefrom, air can pass through the ventilation opening.