An image forming apparatus includes a vibration adjustment unit which adjusts a natural frequency of an optical system, a measuring unit which measures vibrational information indicating change in vibration, and a controller which individually drives each unit. The measuring unit measures the vibrational information after the natural frequency is adjusted to a drive frequency of each unit at an initial state. The controller stores this vibrational information as initial vibrational information. The measuring unit measures the vibrational information after the natural frequency is adjusted to a drive frequency of a unit to be checked. The controller compares this vibrational information with the initial vibrational information measured after adjustment of the natural frequency to the drive frequency of the unit to be checked. The controller determines abnormality in the unit to be checked according to the comparison.