To provide a cutter for print paper, performing cutting independently of the control from a printing part 9 and enabling continuous self-sustaining to improve the general processing speed of printing and cutting.

A detour path 23 or slack of printing paper 2 is provided between the printing part 9 side and the cutting part 15 side by a buffer arm 20, thereby absorbing a difference in cutting speed and printing speed, and the control is conducted so that when slack is eliminated with the progress of cutting, the cutting is once stopped to be on standby until the printing progresses, and when slack again occurs, the cutting is started. Aiming at the above control, this cutter is provided with the buffer arm 20 for causing the printing paper 2 to make a detour to the detour path 23 between the printing part 9 and the cutting part 15, and a tension monitoring part 14 for monitoring the tension of the printing paper 2, wherein when the tension of the printing paper 2 is a predetermined level or lower, the printing paper 2 is cut by the cutting part 15, and when it exceeds the predetermined level, the cutting is temporarily stopped.