Abstract: A folding apparatus for zigzag folding a paper web with a cylinder driven in rotation alternately in one direction and the other. Two folding rollers are biased against the cylinder. A return stop is provided in the end region of the paper web feed. Two jointly pivotal guide members having guide rails arranged in the manner of a rake with free ends being directed towards one another are located upstream of the cylinder. In the lower end position, the guide rails of the upper guide member project into the built-up space defined between the folding rollers and the rotatable cylinder. The upper guide member, together with the lower folding roller, delimit a guide passage for the paper web. In the upper end position, the guide passage for the paper web is formed by the upper folding roller and the guide rails of the lower guide member.