A process for producing a container having spiral ridges on an inner surface thereof, by a machine for producing a container having spiral ridges on an inner surface thereof, wherein the machine comprises a parison forming device for forming a tubular parison having raised ridges on an inner surface thereof, a spiral ridge forming device comprising a clamp for clamping the parison hanging from a die of the parison forming device after extrusion of the parison from the die , and a rotator for rotating the clamp clamping the parison in the circumferential direction of the parison to twist the parison and the raised ridges thereon in the circumferential direction, and a container forming device for inflating the parison having the spiral ridges from the inside thereof to form a container , wherein the spiral ridge forming device comprises a base , a spiral ridge forming unit disposed on the base , a transfer mechanism that moves the base together with the spiral ridge forming unit in the horizontal and vertical directions, a sensor , and a controller that controls the movement of the spiral ridge forming unit and the transfer mechanism , the process comprising a parison forming step of forming a tubular parison having raised ridges on the inner surface thereof, a spiral ridge forming step of converting the raised ridges on the parison obtained in the parison forming step into spiral ridges, and a container forming step of inflating the parison obtained in the spiral ridge forming step from the inside thereof to form a container , the spiral ridge forming step comprising a clamping step of clamping the parison hanging from a die after extrusion of the parison from the die in the parison forming step, and a twisting step of twisting the parison and the raised ridges thereon in the circumferential direction of the parison while the parison clamped in the clamping step being kept clamped. wherein the machine comprises a parison forming device for forming a tubular parison having raised ridges on an inner surface thereof, a spiral ridge forming device comprising a clamp for clamping the parison hanging from a die of the parison forming device after extrusion of the parison from the die , and a rotator for rotating the clamp clamping the parison in the circumferential direction of the parison to twist the parison and the raised ridges thereon in the circumferential direction, and a container forming device for inflating the parison having the spiral ridges from the inside thereof to form a container , wherein the spiral ridge forming device comprises a base , a spiral ridge forming unit disposed on the base , a transfer mechanism that moves the base together with the spiral ridge forming unit in the horizontal and vertical directions, a sensor , and a controller that controls the movement of the spiral ridge forming unit and the transfer mechanism , the process comprising a parison forming step of forming a tubular parison having raised ridges on the inner surface thereof, a spiral ridge forming step of converting the raised ridges on the parison obtained in the parison forming step into spiral ridges, and a container forming step of inflating the parison obtained in the spiral ridge forming step from the inside thereof to form a container , the spiral ridge forming step comprising a clamping step of clamping the parison hanging from a die after extrusion of the parison from the die in the parison forming step, and a twisting step of twisting the parison and the raised ridges thereon in the circumferential direction of the parison while the parison clamped in the clamping step being kept clamped. <EOS>