Image forming apparatus

An image forming apparatus comprising:

• an image support that supports a toner image;
• a transfer member adapted to sandwich with the transfer member and the image support;
• a voltage application unit that applies a transfer bias voltage to the transfer member;
• a first current detecting unit that detects transfer current flowing from the voltage application unit to the transfer material after transfer processing on the transfer material starts;
• a pre-transfer guide member that is provided upstream from the transfer member and is connected to a ground;
• a second current detecting unit that detects guiding current flowing from the pre-transfer guide member to the ground;
• and
• a control unit that acquires values of transfer current and guiding current from the first and second current detecting units, and sets an upper limit of a subtraction value between the transfer current and the guiding current, wherein,
• after the setting of the upper limit of the subtraction value, the control unit further acquires values of transfer current and guiding current from the first and second current detecting units to derive a subtraction value that is to be set during transfer and control a transfer bias voltage generated by the voltage application unit, such that the subtraction value during transfer does not exceed the upper limit.