A (Li, Na, K)(Nb, Ta)O3 based piezoelectric/electrostrictive porcelain composition obtained by adding a slight amount of a Mn compound to a perovskite type oxide containing Li, Na and K as A-site elements and contains at least Nb out of Nb and Ta as B-site elements, where a ratio of a total number of atoms of the A-site elements to a total number of atoms of the B-site elements is not smaller than 1. A composition of the perovskite type oxide as a principal component is represented by a general formula: {Liy(Na1-xKx)1-y}a(Nb1-zTaz)O3. The A/B ratio “a” preferably satisfies 1