PURPOSE: To enable uniform and continuous coating of webs by detecting joint parts of running webs and controlling jumping or turning at specified angle of a doctor knife basing on the detection signal.

CONSTITUTION: Action of a doctor knife 1 is set beforehand by the switching device of a controller 34 according to the kind of web 6. A value corresponding to the length of web between edges 2 of the doctor knife 1 facing a joint detector 31, and the web 6 is set to the setting section of the controller 34. When a joint part 7 of running webs 6 is detected by a detector 31, the output signal is inputted to the body of the controller 34 through a gate to start operation. When the feeding length of webs 6 arrives at the wet value, the controller 34 outputs signals to the turning mechanism 12 and jumping mechanism of the doctor knife 1.