In the $(Pb_{1-x}M_x)[(Mn_{1/3}Sb_{2/3})_{0.05}Zr_yTi_{0.95-y}]O_3$ system, where M=Ca and Sr, the piezoelectric properties were evaluated to examine the possibility of application to piezoelectric transformer. A Rosen-type piezoelectric transformer was formed, then the electrical properties of voltage step-up ratio, frequency characteristics etc. were analysed. The morphotropic phase boundary was determined to be y=0.475 in $Pb[(Mn_{1/3}Sb_{2/3})_{0.05}Zr_yTi_{0.95-y}]O_3$ system and the piezoelectric properties of this composition was kp=0.59, Qm=1600 and $varepsilon_r$=1150. Moreover, when 1-2 mol% of Sr are substituted, enhanced piezoelectric properties of kp=0.61, Qm=1600 and $varepsilon_r$=1400 were shown. The temperature rising (ΔT) of a piezoelectric transformer with $Pb[Mn_{1/3}Sb_{2/3})_{0.05}Zr_{0.475}Ti_{0.475})]O_3 $ composition was $10^{circ}C$, and the voltage step-up ratio was 500 when the output voltage was 4000V, whereas the ΔT was below $3^{circ}C$ and the resonant frequency variation ($Delta f_r$) as a function of load resistance was below 5% when the output voltage was 2000 V. These characteristics are superior to the properties of materials, which were substituted by Ca or without substitution.