An image forming apparatus has an image transferring portion for transferring an image onto a sheet, an image fixing portion for fixing the transferred image to the sheet, a sheet conveyor portion arranged between the image transferring portion and the image fixing portion for conveying the sheet in a sheet conveying direction, a support portion having an elliptical-shaped shaft hole extending in a direction crossing the sheet conveying direction, and an arm rotatably mounted on the support portion. A first spur is disposed at a position opposed to the sheet conveyor portion and is rotatably supported by the support portion and movable along the shaft hole. A second spur is disposed at a position opposed to the sheet conveyor portion downstream in a sheet conveying direction of the first spur and closer to the sheet conveyor portion than the first spur. The second spur is rotatably supported by the arm and has a movable range larger than a movable range of the first spur.