A post-processing apparatus includes: a transport passage on which a sheet that has been sequentially transported from an upstream side is transported; a first transport path on which the sheet that has been transported from the transport passage is transported in a first direction; a second transport path on which the sheet that has been transported from the transport passage is transported in a second direction; a third transport path on which the sheet that has been transported from the transport passage is transported in a third direction; and a guide mechanism that guides the sheet that has been transported from the transport passage, to any of the first, second, and third transport paths, in which the guide mechanism is configured by one switching mechanism.