PURPOSE: To excavate the ground containing large gravel pebbles by oscillating a rotor provided with cutter heads front and rear and fan-likely with cylinders, and discharging excavated lump of rock during excavating after crushing with the rotor.

CONSTITUTION: A pyramid-shaped case 34 is provided on the extreme end of a shield excavating machine 10 having a square section, and therein a rotor 58 provided with cutter heads 66 is provided on a forward eccentric shaft 38 connected with cylinders 50 through links 56. The outer surface of the rotor 58 is formed into a polygonal shape and provided with a plurality of projections 62. Excavating is performed, while oscillating the cutter heads 66 fan-likely by operating the cylinders 50, at the same time excavated large gravel pebbles are crushed between the rotor 58 and the case 34, and discharged through an discharge port 74. Hereby, the ground containing large gravel pebbles can be easily excavated.