PURPOSE: To easily produce a cell structural body which is complicated in shape and thin in wall thickness without causing deformation and breaking due to pressure by making the end face of injection side of a dome-shaped extrusion die to be a concave surface.

CONSTITUTION: This dome-type extrusion die has a concave end face on injection side, and the end face on inflow side is made to be e.g. a convex surface. The dome-shaped extrusion die has a curved or circular cross section and is provided with an inflow part, an injection part and a connection part between both is shown in Fig. (b) as particularly useful example. This die can be formed, for example, by mixing sinterable powders to form a batch, forming the batch into a flat preform shown in Fig. (a), and deforming the preform before or after sintering. Since slots 15 are tapered to become narrower toward the injection side due to the curvature, the slots become narrow in width therein, and so, a honeycomb structure, which is far much thinner in wall thickness than that formed by using the reference die, can be extruded. Further, when the batch passes through the die, the transverse flow increases, and thereby the batch is more properly filled up into the slots 15.