Provided is a process for producing a multilayered ceramic substrate, with which a ceramic substrate having a step portion of a desired shape can be efficiently produced without requiring complicated producing process steps and equipments, as well as a multilayered ceramic substrate having high form precision produced by the process. An auxiliary-layer-lined unfired ceramic body 11, which is provided in a principal surface thereof with a step portion 15, has an unfired ceramic body 10 and an auxiliary layer 20 which is adhered to one principal surface of the unfired ceramic body 10 and which is made of a material substantially unsinterable at a temperature at which the unfired ceramic body 10 is fired. The auxiliary-layer-lined unfired ceramic body is fired at a temperature at which the unfired ceramic body is sinterable but the auxiliary layer is substantially unsinterable, while the auxiliary layer remains adhered to the unfired ceramic body. Pressing operation is performed by using a die 30 having a projection 22 placed on the side of the auxiliary-layer-lined unfired ceramic body retaining the auxiliary layer, so that the step portion (recess) 15(15a), having a shape corresponding to the outer shape of the die projection 22, is formed in the side of the auxiliary-layer-lined unfired ceramic body retaining the auxiliary layer.