To provide a device recycling a paper tube and a residual yarn at a low cost by reducing the troublesomeness required for removing the residual yarn from the paper tube and efficiently continuing the cutting-off works of the residual yarn getting into a thin layer in particular.

This residual yarn cutting-off device for the paper tube is provided with a holder for holding the paper tube, a cutter positioned outer circumference side of the paper tube held by the holder, a traveling device relatively moving the cutter in the axial direction of the paper tube, and an approaching/ separating device approaching/separating the cutter in the radial direction of the paper tube and positioning it. The cutter is provided with a sensor for detecting the outer circumferential face of the paper tube or a stopper, a rotating cutter, a heat cutter, an expansion device pushing and expanding the cut yarn layer toward the left/right between the rotating cutter and the heat cutter, and an energizing device for energizing the edge of the heat cutter towards the paper tube.