Abstract: The invention contemplates to provide a die insert for an extruder, which can suppress the motions of cords at a rubber topping time to improve the disturbance of the cord array pitch of a topping sheet drastically thereby to improve the homogeneity and quality of the topping sheet. In the die insert 1 for the extruder, cord slots 11 are provided at their exit portions with flat faces 14 having channels 11a leading to the cord slots 11 at a die insert leading end portion 12, and the channels 11a for passing a cord array 21 are formed open in the flat faces 14. The channels 11a in the flat faces 14 preferably have a ratio of L/D of 1 to 20 between their open length (L) and diameter (D), and the flat faces 14 are preferably formed to have a step S between the surface side and the back side of the cord array 21.