A piezoelectric/electrostrictive porcelain composition contains at least Nb, Ta, and one or more kinds of alkali metal elements, and a ratio (molar ratio) of Nb, Ta, and the alkali metal element is represented by a non-stoichiometric composition ratio. The piezoelectric/electrostrictive porcelain composition is capable of obtaining a piezoelectric/electrostrictive device which is dense and which is superior in crystallinity and which exhibits superior piezoelectric/electrostrictive characteristics even in a case where the composition is fired on lower-temperature conditions as compared with a conventional technology.