An image forming apparatus includes an image forming device; a fixing device; a first conveyance passage downstream from the fixing device in a sheet conveyance direction; a second conveyance passage downstream from the fixing device and communicating with the first conveyance passage; a sheet reversing member to reverse a conveyance direction of the sheet to the second conveyance passage; a divider to switch a route of the sheet between the first conveyance passage and the second conveyance passage; and a sheet detection sensor disposed downstream from the fixing device and upstream from the divider. The first conveyance passage includes a sheet outlet from which the sheet is ejected outside the apparatus. The apparatus further includes a ventilation passage communicating with an outside, to guide air from the outside to pass the sheet detection sensor and enter at least one of the first conveyance passage and the second conveyance passage.