Abstract: A paper web threading apparatus for a rotary printing press, which occupies a minimum space required for the installation thereof and which enables automatic threading of a paper web to be conducted smoothly without applying any ineffective tension to the paper web which can be guided along all relevant paper web threading paths. The paper web threading apparatus includes a guide path provided along and laterally of the paper web threading path. A paper web guiding member includes a belt-shaped member having a guided end engaging portion adapted to engage with or secure the guided end of the paper web. A guiding member moving and driving device meshs with the paper we guiding member so as to move the latter along the guide path.