An image forming apparatus includes an image bearing member, a transfer member forming a transfer portion, a transfer voltage applying device, a sensor, and a controller. The controller is capable of executing an operation in a first setting mode before a preparatory operation, and executes, in the preparatory operation, an operation in a second setting mode in which test voltages or test currents fewer in number of levels than those in the first setting mode are supplied to the transfer portion and in which a second voltage-current characteristic is acquired on the basis of a first voltage-current characteristic in the operation in the first setting mode and a detection result of the sensor detected during supply of the test voltages or the test currents, and then sets the transfer voltage on the basis of the second voltage-current characteristic.