Image formation apparatus

An image formation apparatus comprising:

• an image carrier;
• a first charging member which abuts on the image carrier and charges the image carrier;
• a second charging member which abuts on the image carrier and charges the image carrier, the second charging member having such resistance characteristics as being less in variation with environmental variation than the first charging member;
• a power supply apparatus which can apply a voltage to each of the first and second charging members;
• and
• a control device which calculates a resistance of said first charging member based on a first amount of current which flows from the power supply apparatus through the first charging member to the image carrier and a second amount of current which flows to the image carrier through the second charging member, and sets a voltage to be applied to the first charging member by the power supply apparatus based on the calculated result.