Abstract: A method of manufacturing a cylindrical billet having a predetermined length useable as raw material for producing a pipe. This method is practiced by way of the steps of drawing a cast slab from a casting mold on a continuous casting stand, spirally winding or cylindrically bending it around a rotating mandrel, joining together both end faces of the wound or bent cast slab to a cylindrical body and cutting it to a predetermined length. Two or more cast slabs may be used for forming the cylindrical body. Two rectangular cast slabs may be used as starting material which are subjected to roll forming and thereafter are cut to the predetermined length. They are then press worked to form a recess having a semi-circular cross-sectional configuration whereby a cylindrical body is constituted by assembly thereof in a superimposed relation.