An image forming apparatus comprises: an image transfer carrying means 18 having flexibility and having an endless sleeve-like shape; a plurality of image forming means 7 which are arranged along the image transfer carrying means 18 such that respective image carriers 17 thereof are in contact with the image transfer carrying means 18, each image forming means 7 comprising a latent image forming means 6 for forming a latent image on the image carrier and a developing means for developing the latent image formed on the image carrier; and transfer bias applying means 16 which are disposed on the back of the image transfer carrying means at positions where the respective image carriers are in contact with the image transfer carrying means for applying transfer bias. The image transfer carrying means 18 is laid around at least two rollers with certain tension and is positioned to be in contact with the image carriers 17 to have predetermined nip width therebetween and each transfer bias applying means abuts the image transfer carrying means 18 to have a contact area narrower than the nip width for applying transfer bias. At gradually increasing spaces at the entrance end and the exit end of each nip portion of the image transfer carrying means, even with high transfer bias voltage, the discharge phenomenon and an undesired phenomenon of toner image scattering from predetermined positions are prevented, thus preventing the deterioration of image quality.