PURPOSE: To easily, reliably, smoothly and beautifully process the end surface of a cut paper tube by R-processing the internal and external circumferences by making an internal/external rounding working tool to come in contact with internal and external circumferences of the end portion after performing a trimming work by making a trimming working tool touck the end of the internal circumference of the cut paper tube.

CONSTITUTION: In order to process the internal circumference side end portion 1a of a cut paper tube 1, first, a trimming working tool 2 is brought in pressure contact with the internal circumference of the internal circumference side end portion 1a while being rotated, for cutting its edged portion. Thereby, a taper 1b is formed on the edged portion, and also burrs 3 of the internal circumference side end portion 1a. Next, a rounding working tool 4 wherein a recessed groove 41 is formed is brought in pressure contact with the end surface of the internal circumference side end portion 1 while being rotated along the end surface shape of the cut paper tube 1. Thereby, the round corners are formed on the internal circumference side 1c and the external circumference side 1d of the end surface rospectively. Accordingly, the internal and external circumference portions of the internal circumference side end portion 1a of the cut paper tube 1 can be smoothly processed.