To adjust the quality of a body to meet the actual conditions for roll molding ceramic products and eliminate complicacy involved in the reuse of a surplus body.

This extruder 14 for the body is equipped with an extrusion screw 32 in the body 30 of the extruder. In addition, a body discharge aperture 38, a first body supply aperture 36, a second body supply aperture 46 positioned beside the first body supply aperture 36 and a vacuum chamber 40 for removing air for the pressure-fed body M to be fed under pressure in the body 30, are provided in the body 30 of the extruder.