To provide a half-splitting cutter, capable of continuously longitudinally splitting a small diameter pipe having the length of 1 m or larger still in a long shape, without cutting the pipe in a length size and making the length of the pipe mutually the same, eliminating the necessity of cutting a pipe in a short length, before half-splitting.

This cutter for half-spliting a small diameter pipe by sending the pipe in the longitudinal direction. The cutter has a pair of front sending disks for sending the introduced pipe forward, a pair of cutting disks for cutting and longitudinally dividing both sides of the pipe, and a pair of rear sending disks for sending the divided-cut pipe forward in a state of being maintained in a cylindrical shape; and is characterized in that these disks are installed in order in the sending direction of the pipe, and a cutting guide bar having a horizontal guide vane concentrically placed with the pipe to be divided in a half-split shape, is arranged between the pair of cutting disks and the pair of rear sending disks.