1. An image-forming device, comprising: an image-forming unit forming an image on a recording medium based on inputted image data; a test image memory storing image data of test image used for calibrating density of image to be formed by the image-forming unit; a test image forming unit controlling the image-forming unit to form the test image by reading image data for test image stored in the test image memory and outputting the image data to the image-forming unit; a density measuring unit measuring the density of the test image that the image-forming unit forms on the recording medium; an abnormality determining unit comparing the density of test image measured by the density measuring unit with prescribed values pre-stored in association with the test images to determine whether the measured density is abnormal; a test image re-forming unit controlling the image-forming unit to re-form test image determined to be abnormal by the abnormality determining unit on the recording medium by outputting image data for the test image determined to be abnormal to the image-forming unit; and a density re-measuring unit measuring the density of the test image that the image-forming unit re-forms on the recording medium.