A reference value of an electric current flowing through each charging member is determined and recorded in a memory unit at a predetermined time by a reference value recording unit. A voltage application unit is caused to start applying a voltage to the charging members upon startup of an image forming apparatus, and a measurement value of an electric current flowing through each charging member is determined by a measurement unit. A charging member of which the measurement value is such that an absolute value of a difference between the reference value and the measurement value is not smaller than a predetermined value is marked by a determination unit. If there is at least one marked charging member and at least one not-marked charging member, a notification produced by a messaging unit is given through a notification unit.