A high-reliability ceramic composite multilayer substrate that has excellent flatness and few remaining pores, can be produced at a low cost while simplifying the manufacturing process, and can eliminate layer separation or separation from a mother board. The ceramic composite multilayer substrate includes a laminate containing a first ceramic layer and a second ceramic layer that is disposed so as to contact the first ceramic layer and suppresses firing shrinkage in the plane direction of the first ceramic layer. The laminate includes a resin/ceramic composite layer in which porous ceramic is impregnated with a resin formed on at least one principal surface of the laminate.