An image formation device in which an image carrier is charged by a charging member includes: a power source configured to supply a charge voltage to the charging member, the charge voltage being formed such that an AC voltage is superimposed on a DC voltage; a detection unit configured to detect an alternating current value flowing through the charging member; and a control unit configured to control a peak-to-peak voltage value of the AC voltage, wherein the control unit executes: first processing of sequentially supplying a plurality of charge voltages from the power source to the charging member in non-image formation; second processing of obtaining, from an alternating current value detection result, a third approximate function indicating a difference value between a first approximate function and a second approximate function; and third processing of determining one of different predetermined ranges and determining a peak-to-peak voltage value in image formation.