1. An image forming apparatus, comprising: a failure prediction unit configured to prepare an index value indicating a condition of the image forming apparatus based on multidimensional signal, obtained by monitoring the image forming apparatus, and to compare the index value with a first threshold value to predict a failure mode of the image forming apparatus; an image identification unit configured to identify types of abnormal images based on the failure mode predicted by the failure prediction unit, an identified abnormal image being predicted to be appear a given time later; a simulated-image generating unit configured to generate a simulated image of the identified abnormal image; and an output unit configured to output the identified abnormal image as the simulated image.