To preform a rubber member which is wider than the discharge opening of a rubber extruder main body without enlarging an extrusion head and a clamp and without causing an icrease in costs while facilitating the extraction of rubber in a rubber channel.

The extrusion head 6 has a head main body part 11 fixed to the rubber extruder main body 3 and a head subordinate part 13 fitted contactably/separably to the front end part 11A of the head main body part 11. A first rubber channel 16 having a circular cross section which extends downstream from the discharge opening 2 of the extruder main body 3 to an intermediate opening 15 having an inside diameter D larger than that of the discharge opening 2 is formed in the head main body part 11. A second rubber channel 18 which is deformed oblongly from an intake 17 having a diameter equal to that of the intermediate opening 15 to a head extrusion opening 5 and makes the width of the head extrusion opening 5 larger than the inside diameter D0 of the discharge opening 2 and equal to or below the inside diameter D1 in the intermediate opening 15 is formed in the head subordinate part 13. A shell clamping means 20 which can clamp the head main body part 11 and the head subordinate part 13 manually and closely connect the first and second rubber channels 16, 18 to each other is provided.

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