An image forming apparatus includes a plurality of optical scanning devices, a job receiver, a job executor, an image discriminator for discriminating whether a formation-target image included in an image forming job is a single-color image or a multi-color image, a first condition judger, a second condition judger and a temperature adjuster. In the case of forming a single-color image, the temperature adjuster drives motors of all the optical scanning devices if a predetermined first condition and a predetermined second condition are satisfied and drives the motor of one optical scanning device and does not drive the motors of the other optical scanning devices but the one optical scanning device if the first condition is satisfied, but the second condition is not satisfied.