To provide a shield machine allowing the translational circular motion of a cutter head stably with a simple structure.

This shield machine is provided with a tubular main body 3, a rotor 7 installed at the front end section of the main body 3 rotatably against the main body 3, a rotatively driving means 25 rotatively driving the rotor 7, a support shaft 15a installed at a position eccentric by the prescribed distance from the rotation center of the rotor 7 rotatably against the rotor 7, a cutter head 15 installed on the support shaft 15a, and rotation restraining means 11, 19, 29 restraining the rotation of the support shaft 15a so that the cutter head 15 makes a translational circular motion when the rotor 7 is rotated.