To provide a manufacturing method of a composite ceramics which hardly generates cracks and favorably densified, a composite ceramics, and a ceramic filter assembly in which a porous ceramic is densely connected to a filter components such as a connector etc.

By this method, the fine pores of a porous ceramic 28 is impregnated with a solution of polysilazane having a repeated structure of base units of [-Si(H)(CH3)-NH-] and [-Si(CH3)2-NH-], and the polysilazane is converted to a silicon nitride ceramic. Since crosslinking and polymerization reaction of the polysilazane during drying and sintering is retrained, its volume contraction is also restrained and hardly causes cracks, and as a result of the restraining of the crosslinking and polymerization reaction, a polysilazane of high molecular weight as high as 1,300 (g/mol) can be used, and the increase in porosity by generation of voids accompanying the evaporation of a solvent in the drying and sintering processes can be restrained.