A sheet processing apparatus includes a transport path for transporting a sheet in a predetermined transport direction; a folding unit disposed along the transport path to perform folding processing on a sheet transported through the transport path; and a downstream-side unit disposed on a downstream side in the transport direction along the transport path to perform processing on a sheet transported from the folding unit. The folding unit includes a space section disposed at a lower side of the transport path for forming a cylindrical shape on a sheet; a transport roller disposed in the transport path to transport a sheet to the space section; and folding rollers to form a fold at a predetermined position on a sheet in which the cylindrical shape is formed. The space section is provided in a range of overlapping the downstream-side unit in a height direction orthogonal to the transport direction.