An image forming apparatus has a plurality of image carriers, a common drive source which drives the plurality of image carriers and a drive shaft that is connected to and driven by the drive source. It also has a plurality of worm gears that are provided corresponding to the plurality of image carriers and are formed coaxially with the drive shaft, and a plurality of worm wheels that are respectively meshed with the respective worm gears and respectively transmit drive forces of the worm gears to the image carriers. The plurality of worm gears are made of a resin material, and the worm gears and the worm wheels drive the plurality of image carries by making use of the elastic deformation of the worm gears when the worm gears and the worm wheels are respectively meshed with each other.