PURPOSE: To make the flow rate of gas uniform by forming a title body in such a manner that either the inlet side end face or outlet side end face has a non-plane shape and that the spacing between the inlet side end face and the outlet side end face is made gradually shorter from the central part toward the peripheral part.

CONSTITUTION: A carrier 1 has the shape in which both bases of the circular column project in a circular conical shape to both sides. A ceramic coating layer 13 is provided on the outside cylindrical surface of such carrier 1. An exhaust gas flows from the inlet side end face 19 into an inlet hole 21 and enters an outlet hole 22 after the passage through a partition wall 18. The gas is discharged from the outlet side end face 20. The harmful components in the exhaust gas are removed by the contact with the catalyst deposited on the surface of skeleton 14 during this time. The flow rate of the gas is made uniform by forming the body into such a shape, by which the flow rate of the gas is made uniform and the entire part of the structure is effectively used.