To minimize the processing time for making a crease on a sheet with an image formed thereon.

A sheet processing device comprises: a creasing part that makes a crease on a sheet with an image formed thereon, in advance, in a position where a fold is to be formed by fold processing; a folding part that forms a fold on the sheet with the image formed thereon by the fold processing; and a control part that controls the creasing and folding processing. The control part checks whether there is an image in the position to be folded on the sheet, decides whether to make a crease on the basis of the presence of the image, and controls whether to make a crease before folding the sheet, on the basis of the above decision.