PURPOSE: To prevent the generation of paper clogging due to a fall of a cut tail end in the case where a delivered web is cut by a cutting device in a flying type automatic paper joining device, which automatically joins a paper with a new roll when a former roll under the delivery condition comes close to the end thereof and continues the operation.

CONSTITUTION: An auto paster controller 19 for measuring a differential quantity between the cutting signal, which is output per each space cut from a cutting device 18, and the position signal, which is output from a position sensor 11 for detecting the tip of a web, and for computing the position of the next position signal and the cutting signal on the basis of a diameter of a new roll and for setting the operation timing in relation with a cutter is provided. A tail end, which is left as it is not cut in the rear from a joint part of the web, is folded by a folder.