PURPOSE: To make possible to produce carbon black in a sufficiently stably usable state for a long period by constructing furnace walls in a combustion zone and a narrow diameter part with a specific oxide-based ceramic refractory material.

CONSTITUTION: Furnace walls of a combustion zone and (a part of) a narrow diameter part for producing carbon black are constructed with an oxide-based ceramic refractory material composed of (A) a zirconia/hafnia-based refractory material having a two-layered structure, (partially) stabilized with a stabilizing agent composed of oxide of calcium, magnesium, yttrium and/or cerium, (B) a zirconia refractory material having a two-layered structure made by laminating a (partially) stabilized zirconia substance layer containing yttria and a (partially) stabilized zirconia substance layer containing calcium oxide in one body, or (C) an alumina/yttria-based refractory having a two-layered structure made by laminating an alumina layer and an yttria layer in one body.