PURPOSE: To perform high-efficient discharge of soil by means of comparatively low pressure feed water.

CONSTITUTION: An excavating pipe 2 is coupled to a connection pipe 3 to form a spindle. A plurality of excavating bits are arranged at intervals K for discharge to the tip of the excavating pipe 2. A contraction pipe contracted toward a tip is connected to the excavating pipe 2. Further, a water feed means, such as a pump, is connected to the rear end of the spindle. Water delivered from the rear end of the spindle increases a velocity of flow by means of the contraction pipe and is jetted with a force and high-efficiently discharged through a gape between the excavating bits together with soil.