Abstract: The present rotary extruder includes: a rotor having a cylindrical surface centered on a rotor axis extending in a horizontal direction; and a casing having an inner peripheral surface that defines a bore, wherein: the casing defines an input port into which a resin material including a thermoplastic resin is fed, and a discharge port from which a plasticized molten resin is discharged; the cylindrical surface of the rotor and the inner peripheral surface of the casing are arranged eccentric with each other, thereby forming a gap whose cross section is crescent-shaped, extending in a rotation direction of the rotor from the input port to the discharge port between the inner peripheral surface and the cylindrical surface; and the input port is arranged at a top portion of the casing and the discharge port is arranged at a lower portion of the casing.