PURPOSE: To prevent a copy from being interrupted, by informing a fact that a web is completed on the way of the copy in advance when the scheduled quantity for using the web has exceeded the remaining length of the web at the time of using the copy.

CONSTITUTION: In an intermediate position of a driven shaft 8 and a press- contacting roller 10, a detecting roller 11 comes into contact with the web 7 in a state that a slide is not generated between said roller 11 and the web 7, and supported so as to be freely rotatable. To the detecting roller 11, shaft 13 of an encoder 1 for rotating together therewith is connected. This encoder 1 generates a pulse signal corresponding to the speed of revolution of the shaft 13, so that this signal is brought to arithmetic processing by a CPU 2 and the remaining length of the web is calculated. Also, the CPU 2 converts the scheduled length for using the web from a copy size and the number of copy sheets to be set inputted at the time of using a copy, and it is set so as to execute warning by lighting or flickering a warning pilot lamp 4 when the scheduled length for use has exceeded the remaining length.