An image forming apparatus includes an image forming device for forming a toner image on an image bearing member, a transfer member for transferring the toner image from the image bearing member onto a transfer material by being supplied with a bias voltage, a bias voltage application device for applying a normal bias voltage of a polarity opposite to that of toner or a reverse bias voltage opposite in polarity to the normal bias voltage, a controller for controlling the bias voltage application device, and integral current detector for detecting an integral of an amount of a current flowing from the bias voltage application device to the transfer member. The integral current detector is capable of detecting an integral current amount of the normal bias voltage at the time of applying the normal bias voltage and an integral current amount of the reverse bias voltage at the time of applying the reverse bias voltage. The controller controls the bias voltage application device so that an absolute value of the integral current amount of the reverse bias voltage is in the range of not less than 0.2% and less than 25% of an absolute value of the integral current amount of the normal bias voltage.