An image forming apparatus comprising: a plurality of image bearing members (2a-2d) configured to bear toner images; a rotatable endless intermediate transfer belt configured to secondarily transfer onto a transfer material the toner images primarily transferred from the plurality of image bearing members (2a-2d); a secondary transfer member configured to contact an outer circumferential surface of the intermediate transfer belt to form a secondary transfer section with the intermediate transfer belt; and a secondary transfer power supply configured to apply a voltage to the secondary transfer member, wherein the intermediate transfer belt is provided with electrical conductivity capable of passing a current from a contact position of the secondary transfer member in the rotational direction of the intermediate transfer belt to the plurality of image bearing members (2a-2d) via the intermediate transfer belt, and wherein the secondary transfer power supply applies a voltage to the secondary transfer member to pass a current from the secondary transfer member to the plurality of image bearing members (2a-2d) via the intermediate transfer belt to generate electric discharge between the intermediate transfer belt and the image bearing members (2a-2d) at a position on the upstream side of the upstream end of a contact position between the intermediate transfer belt and the image bearing member at each of a plurality of primary transfer sections in the rotational direction of the intermediate transfer belt, such that a potential difference between the intermediate transfer belt and the image bearing members (2a-2d) at the contact position is smaller than a Paschen discharge threshold voltage value. a plurality of image bearing members (2a-2d) configured to bear toner images; a rotatable endless intermediate transfer belt configured to secondarily transfer onto a transfer material the toner images primarily transferred from the plurality of image bearing members (2a-2d); a secondary transfer member configured to contact an outer circumferential surface of the intermediate transfer belt to form a secondary transfer section with the intermediate transfer belt; and a secondary transfer power supply configured to apply a voltage to the secondary transfer member, wherein the intermediate transfer belt is provided with electrical conductivity capable of passing a current from a contact position of the secondary transfer member in the rotational direction of the intermediate transfer belt to the plurality of image bearing members (2a-2d) via the intermediate transfer belt, and wherein the secondary transfer power supply applies a voltage to the secondary transfer member to pass a current from the secondary transfer member to the plurality of image bearing members (2a-2d) via the intermediate transfer belt to generate electric discharge between the intermediate transfer belt and the image bearing members (2a-2d) at a position on the upstream side of the upstream end of a contact position between the intermediate transfer belt and the image bearing member at each of a plurality of primary transfer sections in the rotational direction of the intermediate transfer belt, such that a potential difference between the intermediate transfer belt and the image bearing members (2a-2d) at the contact position is smaller than a Paschen discharge threshold voltage value.