An image forming apparatus includes an image bearing member, an intermediary transfer belt, a transfer member, a voltage source for applying a voltage to the transfer member, a detecting portion for detecting a current flowing through the transfer member, and a controller for carrying out constant-voltage control so that the voltage applied to the transfer member becomes a target voltage when a recording material P passes through a transfer portion. The controller is capable of changing the voltage applied to the transfer member so that a detection result detected by the detecting portion during transfer falls within a predetermined range. The controller changes the predetermined range on the basis of the detection result detected by the detecting portion when the voltage is applied to the transfer member in a state in which the recording material P is absent in the transfer portion.