To cut reinforcements such as vertical reinforcements buried to an existing pipe made of reinforced concrete efficiently and surely by installing a vertical-reinforcement bending means in a small-bore pipe excavator laying a new pipe while crushing the existing pipe.

Notch type roller cutters 12, 12 are mounted rotatably on a cutter head 10 set up to the leading pipe 3 of a small-bore pipe excavator, and the vertical reinforcements of an existing pipe projected from a cut surface are bent forcibly in the direction of rotation of the cutter head 10 from the roots of the vertical reinforcements by the web sections of the notches of the roller cutters 12, and cut by the edge sections of the notches. The reinforcements are bent forcibly in the direction of rotation of the cutter head 10 by a cutter- head face plate or a roller and cut by a gear type roller cutter as another plan. The cutter-head face plate is formed in a projecting or recessed conical shape, and the vertical reinforcements may also be bent. Accordingly, the vertical reinforcements can be cut efficiently and surely by forcibly bending the vertical reinforcements of the existing pipe projected from the cut surface.