A post-processing apparatus including: a first conveyance section which superposes a plurality of paper sheets conveyed from an image forming apparatus, and conveys with superposed state; a second conveyance section which conveys the paper sheets, sheet by sheet; a switching section which switches to convey the paper sheets either to the first or to the second conveyance section; a punch processing section which temporally stops the paper sheets from the first or the second conveyance section, and forms punch holes on the paper sheets; and a control section, wherein if determined, based on the basis weight or thickness information of the paper sheet, that the punch processing is not executable on the paper sheets with the superposed state, the control section controls to convey the paper sheets into the second conveyance section, and to execute the punch processing sheet by sheet.