To provide a sprue for extrusion which can easily reproduce the shape of the opening part of a sprue in accordance with the cross-sectional shape of the rubber member to be extruded.

A sprue body 10 deciding the cross-sectional shape of a rubber member 2 extruded from an extruder is composed of: a lower sprue member 11 forming the side of the bottom face 2a in the rubber member 2; and an upper sprue member 12 obtained by superimposing a plurality of sheet metals 12k to the thickness direction thereof. Further, the sprue includes: a rising and falling means 30 having a clamp pawl 31 clamping each sheet metal 12K in the upper sprue member 12 from the side thereof and a vertical movement mechanism 33 vertically moving the clamp pawl 31; and a moving means 40 moving the rising and falling means 30 to the width direction of the rubber member 2. Each sheet metal 12K is slid to the upper part by a prescribed height, so as to form an opening part 12S deciding the cross-sectional shape of the rubber member 2 between the upper sprue member 12 and the lower sprue member 11, and the rubber member 2 is extruded from the opening part 12S.