A piezoelectric/electrostrictive ceramic composition containing, as a major component, a Pb(Mg.sub.1/3Nb.sub.2/3)O.sub.3--PbTiO.sub.3--PbZrO.sub.3 ternary solid solution system composition and further containing Ni in an amount of 0.05 to 3.0% by mass in terms of NiO and Si in an amount of 0.003 to 0.01% by mass in terms of SiO.sub.2. The piezoelectric/electrostrictive ceramic composition can constitute a piezoelectric/electrostrictive body or a piezoelectric/electrostrictive portion both having an excellent piezoelectric/electrostrictive property and durability even under high-temperature and highly humid conditions.