A developing agent image is formed by adhering a developing agent onto an electrostatic latent image formed on an image holding material and transferred onto an image forming medium, thereby forming an image. A resistance value ratio of a resistance value of a transfer member arranged so as to face the image holding material when a voltage 1000 V is applied to the transfer member to a resistance value when a voltage 500 V is applied is set to (0.5.ltoreq.ratio.ltoreq.0.89). Likewise, a resistance value ratio of a resistance value when 2000 V is applied to that when 1000 V is applied is set to (0.3.ltoreq.ratio.ltoreq.0.88). Since a just enough transfer current can be optimally generated, image quality can be improved and an image forming apparatus which does not need a large-capacity power source and an elastic roller are provided.