A processing object modifying apparatus includes a conveying unit that conveys a processing object; a plasma processing unit that performs plasma processing onto a surface of the processing object while the processing object is being conveyed by the conveying unit; a measuring unit that measures a pH value of the processing object to which the plasma processing has been applied; and a controlling unit that controls the conveying unit to change a conveying speed of the processing object on the basis of a measurement result of the measuring unit, the processing object to which the plasma processing is being applied.