A post-processing device includes a transport path along which a medium printed with liquid ejected by a liquid ejecting portion is transported, an intermediate tray on which the medium is stacked, a first transporting member starting a first transporting operation of transporting the medium upstream in a transport direction after a rear end of the medium passes through the transport path, a rear-end alignment portion that comes into contact with the rear end of the medium transported by the first transporting member and that aligns the medium, a control portion controlling an operation of the first transporting member, and a detection portion detecting a transporting state of the medium in the intermediate tray, in which when the control portion determines, from an output of the detection portion, that the medium reaches the rear-end alignment portion, the control portion regulates the first transporting operation of the first transporting member.