a developing device is opposed to a photosensitive drum which is rotated in one direction , and develops a latent image formed on the photosensitive drum . the developing device is provided with a first developing roller which is rotatably arranged to oppose the photosensitive drum and holds a first developing agent , and a second developing roller which is rotatably arranged to oppose the photosensitive drum , located adjacent to the first developing roller along one direction and holds a second developing agent . the first developing roller is rotated in one direction , to supply the first developing agent onto the photosensitive drum , and the second developing roller is rotated in a direction opposite to the direction to supply the second developing agent onto the photosensitive drum .