Folding device (1) for folding a packaging, which is substantially closed in its peripheral direction, from a sheet (19) of a foldable material, comprising a surface (2,21,3,22) which is horizontal in the situation of use and which is provided with an elongate channel (5) with a predetermined with and depth for receiving and deforming a sheet (19) of a foldable material laid on this surface, wherein the width and the depth of the channel (5) are determined by the peripheral dimensions of the packaging for folding, wherein the channel is provided with engaging means (6,7) displaceable in vertical direction for engaging a sheet (19) laid on the surface (2,21,3,22) and extending over the channel (5) and for receiving and deforming said sheet (19) in the channel by downward displacement of said engaging means (6,7).