An image forming apparatus includes a fixing device for thermally fixing the image on the recording medium; a medium type detection unit for detecting a type of recording medium; a temperature adjusting unit for adjusting a temperature of the fixing device according to the type of recording medium; and a storage unit for storing data indicating the type of recording medium. The temperature adjusting unit sets a target temperature according to the type of recording medium stored in the storage unit and starts heating the fixing device. After the temperature adjusting unit sets the target temperature and starts heating the fixing device, the temperature adjusting unit determines whether to change the target temperature according to a comparison result between a type of recording medium newly detected by the medium type detection unit and the type of recording medium indicated by the data stored in the storage unit.