To provide a foreign matter-removing device which can almost completely remove a foreign matter in a pipe installed in underground having a medium or small diameter, especially a vegetative root entering from a defective spot or the like, along an inner wall face of the pipe and is small in a diameter easy in operation.

A removing device for a foreign matter in a pipe installed in the underground is at least equipped with a cutter driving motor 2 detachably mounted on a slidable frame 1; a cylindrical rotary cutter 4 which is fixed to the shaft of a motor and has a serrated cutter in a front end part; a plurality of sub-cutters 5 supported by the rotary cutter 4 so as to be able to protrude outward from an accommodating position in the outer periphery of the rotary cuter 4; and a tracting rope attachment rotatably provided at the front end in an axial position of the rotary cutter 4, or the removing device is equipped with a polishing cutter which is composed of a plurality of polishing tools formed of bundle-shaped metal wires and vibraticngly and suspendibly attached to the outer periphery instead of the rotary cutter 4.