An image forming apparatus includes an image forming section, a fixing section, a detector, and a controller. A recording medium has a first surface and a second surface. A pair of marks is formed on the second surface with ink that becomes transparent at a specific temperature or higher. The controller calculates a distance between the marks based on a detection result of the detector after the fixing section has fixed toner to the first surface. The controller calculates a shrinkage of the recording medium based on the calculated distance. The image forming section forms an image on the second surface according to the shrinkage. The fixing section fixes the toner to the first surface at a first fixing temperature which is lower than the specific temperature. The fixing section fixes the toner to the second surface at a second fixing temperature which is higher than the specific temperature.