PbTiO$_3$ thin films were prepared by low-pressure thermal plasma deposition on (100)Pt/(100)MgO substrates. Mist of source material in which metal alkoxides are dissolved in 2-methoxyethanol was introduced into plasma through heating furnace and deposited onto substrates at $600^{circ}C$. As-deposited PbTiO$_3$/Pt/MgO thin film prepared at 1.33$ imes$10$^4$ Pa was grown epitaxially, but was consisted of many rectangular shaped grains, with many grain boundaries and it was impossible to measure electric properties. As-deposited film prepared at 1.00$ imes$10$^4$ Pa showed weak peaks of X-ray diffraction and the film was not grown epitaxially. On the other hand, the film after annealed at $700^{circ}C$ showed strong diffraction peaks and epitaxial growth was also observed. For annealed film, moreover, no clear grain boundaries were observed. The value of ${varepsilon}_r$, tan${delta}$, Pr and Ec of annealed film were 160, 3.2%, 10.4${mu}$C.cm$^-2$ and 51.2kV.cm$^-1$, respectively. Since the composition, Pb/Ti, measured by EDS attaching to SEM changed point by point, the distribution of composition in annealed film was investigated and found out several relations between composition and electric properties. At stoichiometric composition, Pr and Ec showed the lowest value and they gradually became large as composition deviated from stoichiometric one. Moreover, the value of ${varepsilon}_r$ became gradually large as the ratio of Ti became high.