A die assembly employed for production of multilayer extrusions each having such a core-sheath structure that a core material is covered with a sheath material on the outer periphery thereof, comprising: a core material supply port supplied with said core material; a sheath material supply port supplied with said sheath material; a plurality of extrusion portions having core material extruding passageways (271a, 272a) located on the central portions thereof for guiding said core material in an extrusive direction and sheath material extruding passageways (141, 142) located on outer peripheral portions thereof for guiding said sheath material in the extrusive direction for covering the outer periphery of said core material with said sheath material and extruding the materials; a core material feed passage guiding said core material from said core material supply port to the core material extruding passageways (271a, 272a) of said extrusion portions; and a sheath material feed passage guiding said sheath material from said sheath material supply port to the sheath material extruding passageways (141, 142) of said extrusion portions, characterized in tat said plurality of extrusion portions are at least partially arranged on at least two concentric circles having different diameters in plural sets respectively, said core material feed passage has a core material feeding layer planarly spreading to communicate with the core material extruding passageways (271a, 272a) of all said extrusion portions and a core material feed pipe having a first end connected onto the central axis of said concentric circle of said core material feeding layer and a second end connected to said core material supply port, and said sheath material feed passage has a sheath material feeding layer planarly spreading to communicate with the sheath material extruding passageways (141, 142) of all said extrusion portions and a sheath material feed pipe having a first end communicating with the central axis of said concentric circle of said sheath material feeding layer and a second end connected to said sheath material supply port. a core material supply port supplied with said core material; a sheath material supply port supplied with said sheath material; a plurality of extrusion portions having core material extruding passageways (271a, 272a) located on the central portions thereof for guiding said core material in an extrusive direction and sheath material extruding passageways (141, 142) located on outer peripheral portions thereof for guiding said sheath material in the extrusive direction for covering the outer periphery of said core material with said sheath material and extruding the materials; a core material feed passage guiding said core material from said core material supply port to the core material extruding passageways (271a, 272a) of said extrusion portions; and a sheath material feed passage guiding said sheath material from said sheath material supply port to the sheath material extruding passageways (141, 142) of said extrusion portions, characterized in tat said plurality of extrusion portions are at least partially arranged on at least two concentric circles having different diameters in plural sets respectively, said core material feed passage has a core material feeding layer planarly spreading to communicate with the core material extruding passageways (271a, 272a) of all said extrusion portions and a core material feed pipe having a first end connected onto the central axis of said concentric circle of said core material feeding layer and a second end connected to said core material supply port, and said sheath material feed passage has a sheath material feeding layer planarly spreading to communicate with the sheath material extruding passageways (141, 142) of all said extrusion portions and a sheath material feed pipe having a first end communicating with the central axis of said concentric circle of said sheath material feeding layer and a second end connected to said sheath material supply port.