1. A printing apparatus comprising: a plasma processing unit that processes a surface of a processing object by using plasma; a recording unit that forms a first-color image on the surface of the processing object by inkjet recording, the surface being plasma-processed by the plasma processing unit, and forms a second-color image to be superimposed on the first-color image by the inkjet recording; and an adjusting unit that adjusts a plasma energy amount that is to be applied to the processing object according to the second-color image.