Image forming apparatus

An image forming apparatus comprising:

• an image bearing member configured to bear a toner image;
• a transfer member configured to transfer the toner image from said image bearing member onto a recording material at a transfer portion under application of a voltage;
• a voltage source configured to apply a voltage to said transfer member;
• a sensor configured to detect a current flowing when the voltage is applied to said transfer member by said voltage source;
• an acquiring portion configured to acquire an index value correlating with a toner amount of the toner image transferred onto the recording material at the transfer portion;
• an information storing portion configured to store correction information, determined in advance for each index value, for correcting a detection result of said sensor depending on the index value;
• and
• a controller configured to adjust the voltage applied to said transfer member,
• wherein during continuous image formation for continuously forming images on a plurality of recording materials, the detection result is corrected on the basis of the detection result of said sensor in a detection period in which a current recording material passes through the transfer portion, the index value relating to the toner image transferred onto a detection region passing through the transfer portion in the detecting period, and the correction information, and then on the basis of the corrected value of the detection result, said controller controls the voltage applied to said transfer member for a subsequent recording material passing through the transfer portion.