According to one embodiment, a sheet separator has a first driving roller and a pressing body. The first driving roller rotates about a first rotation shaft. The first driving roller conveys a sheet bundle including a plurality of sheets. The pressing body is capable of approaching the first driving roller. The first driving roller is rotatable in a first direction with the sheet bundle sandwiched between the first driving roller and the pressing body. The pressing body pivots in the first direction about the first rotation shaft with the sheet bundle sandwiched between the first driving roller and the pressing body to cause the plurality of sheets to deviate from one another at edges.

According to an example aspect of the present invention, there is provided a method and apparatus for folding a stack of superposed sheets. The method comprises transferring the stack to a folding station, gripping a first part of the stack with a first grip and forming a crease on the stack to facilitate the folding. Then the at least a part of the stack is folded over the first part of the stack that has been gripped by utilizing the crease, the folded stack is gripped with a second grip and the folded stack is transferred from the folding station to a next handling stage and releasing the first grip.