PROBLEM TO BE SOLVED: To provide a web supplying device which can reduce an installation space, have a simple structure and be controlled of maintenance easily without changing the obverse and the reverse surface of the web supplied continuously. SOLUTION: The delivery of the web of a web roll 2 is switched by using a device which delivers the web 3 continuously by an automatic web connecting device 30. An arm 12 which supports the web roll 2 is fluctuated. The remaining core 6 of a web roll 2a is removed after switching from one web roll 2a to the other web roll 2b. Then a new web roll 2a' is attached to the position of a web roll installation after the position is moved on the reverse side to the obverse and the reverse surface of the web 3 which being delivered from the web roll 2b. The remaining core 6 of the web roll 2b is removed after switching from other web roll 2b to one web roll 2a. Then a new web roll 2b' is attached to the position of the web roll installation on the same side to the obverse and the reverse surface of the web 3 which being delivered from the web roll 2a, and the web 3 is supplied continuously.