There is disclosed a piezoelectric/electrostrictive body in which a polarization direction of a domain indicates reversible conversion in an electric field and a strain ratio increases, a manufacturing method of the same, and a piezoelectric/electrostrictive element. The piezoelectric/electrostrictive body includes a matrix phase represented by a composition formula ABO3, and an additional, material phase included in the matrix phase, having at least a crystal structure of tetragonal system, represented by a composition formula ABO3 and having a composition different from that of the matrix phase. For example, an alkali-niobate-based material of the tetragonal system, BaTiO3, PZT, PbTiO3, or (Bi0.5, Na0.5)TiO3 is added as an additional material forming the additional material phase to an alkali-niobate-based matrix material forming the matrix phase to form the piezoelectric/electrostrictive body. An amount of the additional material to be added has a volume ratio of 5 vol % or more and 30 vol % or less (5 vol % or more and 45 vol % or less in a case where an additional material having a composition to which Mn has been added is used) with respect to the matrix material.