An image forming apparatus includes an image forming device for forming a toner image on an image conveying member on the basis of an input image signal; a transfer device for transferring the toner image from the image conveying member onto an image receiving member; a bias applying device for applying a transfer bias to the transfer device when the toner image is transferred from the image conveying member onto the image receiving member; an executing portion for executing a test mode in which a test image is formed on the image conveying member and is then transferred onto the image receiving member; a detecting device for detecting a current passing through the transfer device in the test mode; a control device for controlling an image forming condition of the image forming device on the basis of an output of the detecting device; and a setting device for setting a test bias to be applied from the bias applying device at a value larger than the transfer bias in terms of an absolute value.