A monolithic piezoelectric element includes an element assembly in which internal electrode layers and piezoelectric ceramic layers are laminated alternately. The internal electrode layers contain an Ag—Pd alloy, which has an Ag content of 85 percent by weight or more as a primary component, a metal element having a valence of at least one of pentavalence or hexavalence. The piezoelectric ceramic layers contain a composite oxide represented by Pb(Ti,Zr)O3 as a primary component, a part of Ag contained in the internal electrode layers is almost uniformly diffused therein and, the metal element is diffused in the form of a metal oxide in such a way that the concentration is reduced with decreasing proximity to the internal electrode layers. In this manner, a monolithic piezoelectric element having a desired large piezoelectric constant can be obtained without inviting an increase in cost even when a firing treatment is conducted at low temperatures.