Image forming apparatus

An image forming apparatus comprising:

• an image bearing member;
• a charging portion that charges the image bearing member;
• an exposure portion that exposes a surface of the charged image bearing member;
• a developing portion that forms a toner image on the image bearing member by supplying toner to an electrostatic latent image formed on the surface of the image bearing member;
• a voltage application member that applies a voltage to the image bearing member in response to a voltage applied thereto;
• a voltage application portion that applies the voltage to the voltage application member;
• a current detection portion that detects a current value flowing through the image bearing member;
• a potential detection portion that determines a surface potential of the image bearing member on the basis of an applied voltage value of a detection voltage applied to the voltage application member by the voltage application portion and a detected current value detected by the current detection portion in response to the applied voltage;
• and
• a control unit that sets an image formation condition for performing image formation in order to form the toner image on the image bearing member on the basis of the surface potential determined by the potential detection portion,
• wherein, when the surface potential is determined by the potential detection portion, the voltage application portion applies the detection voltage after applying, to the voltage application member, a voltage having an opposite polarity to an image formation voltage that is applied to the voltage application member during image formation.