A rubber extruder for pressurizing and kneading inputted rubber, comprising: a cylinder and a screw arranged in the cylinder, the cylinder having an inlet side and an outlet side, and a sampling device mounted on an outlet-side end portion of the cylinder and having a center hole which becomes a path for rubber extruded from the cylinder at the center part and a rubber sample taking-out path on an inner peripheral surface of the center hole, respectively, and provided with a path opening/closing means which opens/closes the rubber sample taking-out path; wherein: respective diameters of the cylinder and the screw are gradually reduced from the inlet side toward the outlet side, the outlet side end portion of the screw reaches the vicinity of a rubber taking-in port of a pair of gears of a gear pump, the gears arranged on gear shafts, a shaft (14) of the screw is inclined with respect to a line connecting the gear shafts, and the sampling device has a surface on a cylinder side thereof and a surface on a gear pump side, the surface on the cylinder side perpendicular to the shaft (14) of the screw and the surface on the gear pump side in parallel with a mounting surface of the gear pump on the cylinder side of the gear pump in a sectional shape thereof, the sampling device forming a substantially triangular shape, and the screw proj ecting from the cylinder penetrates the center part of the sampling device. a cylinder and a screw arranged in the cylinder, the cylinder having an inlet side and an outlet side, and a sampling device mounted on an outlet-side end portion of the cylinder and having a center hole which becomes a path for rubber extruded from the cylinder at the center part and a rubber sample taking-out path on an inner peripheral surface of the center hole, respectively, and provided with a path opening/closing means which opens/closes the rubber sample taking-out path; wherein: respective diameters of the cylinder and the screw are gradually reduced from the inlet side toward the outlet side, the outlet side end portion of the screw reaches the vicinity of a rubber taking-in port of a pair of gears of a gear pump, the gears arranged on gear shafts, a shaft (14) of the screw is inclined with respect to a line connecting the gear shafts, and the sampling device has a surface on a cylinder side thereof and a surface on a gear pump side, the surface on the cylinder side perpendicular to the shaft (14) of the screw and the surface on the gear pump side in parallel with a mounting surface of the gear pump on the cylinder side of the gear pump in a sectional shape thereof, the sampling device forming a substantially triangular shape, and the screw proj ecting from the cylinder penetrates the center part of the sampling device. respective diameters of the cylinder and the screw are gradually reduced from the inlet side toward the outlet side, the outlet side end portion of the screw reaches the vicinity of a rubber taking-in port of a pair of gears of a gear pump, the gears arranged on gear shafts, a shaft (14) of the screw is inclined with respect to a line connecting the gear shafts, and the sampling device has a surface on a cylinder side thereof and a surface on a gear pump side, the surface on the cylinder side perpendicular to the shaft (14) of the screw and the surface on the gear pump side in parallel with a mounting surface of the gear pump on the cylinder side of the gear pump in a sectional shape thereof, the sampling device forming a substantially triangular shape, and the screw proj ecting from the cylinder penetrates the center part of the sampling device.