Disclosed is a ceramic multilayer substrate which is obtained by co-sintering a low dielectric constant layer, which is composed of an insulating material having a low dielectric constant, and a high dielectric constant layer, which is composed of a dielectric material having a high dielectric constant. The low dielectric constant layer contains a low dielectric constant ceramic component having a composition represented by the following formula: xBaO-yTiO2-zZnO (wherein x, y and z each represents a molar ratio, while satisfying x + y + z = 1, 0.09 <= x <= 0.20, 0.49 <= y <= 0.61 and 0.19 <= z <= 0.42) and a boron oxide-containing glass component which is added in an amount of not less than 1.0 parts by weight but not more than 5.0 parts by weight per 100 parts by weight of the low dielectric constant ceramic component. The high dielectric constant layer is composed of a barium titanate dielectric material to which CuO and Bi2O3 are added.