TUNNELING MACHINE

PROBLEM TO BE SOLVED: To provide a cutter for sensing an obstruction which can be easily mounted without changing the shape of a conventional tunneling machine and can precisely grasp the presence and the shape of an obstruction and can also prevent beforehand damage to an earth-sand cutting cutter. SOLUTION: Cutter bits 6 and a plurality of obstruction sensing cutters 8 extending forward of preceding cutters 7 are provided on the front side of a cutter head and a strain gauge is provided in the cutter head. When the cutters 8 contact an obstruction, the gauge captures the force generated at the contact as a variation in external loads and a signal of the variation is inputted into a control device. The control device judges whether the variation in external loads is caused by a gravel or by an obstruction such as a pile and grasps the shape and location of the obstruction.