Abstract: Repetition of a process of impregnating a metal fiber or ceramic fiber preform or porous ceramic with (3) a mixture of polysilazane-type polymers with a number average molecular weight of 200-3000 and a viscosity adjusted to 100 Pa.s or lower at the impregnation temperature, prepared by mixing (1) one or more types of polysilazane-type polymers with a number average molecular weight of 200-3000 and a viscosity of less than 1 Pa.s at the impregnation temperature with (2) one or more types of polysilazane-type polymers with a number average molecular weight of 200-100,000 and having a viscosity of 1 Pa.s or higher or solid at the impregnation temperature, which are selected from polysilazanes whose main repeating unit is --[(SiH.sub.2).sub.n (NH).sub.r ]-- (where n and r are 1, 2 or 3), and copolymers, modified polymers and crosslinked polymers based thereon, and performing crosslinking curing and then firing, is performed for its conversion into a ceramic.