We report locally crystallized ferroelectric nanodots in a noncrystallized PbTiO3 thin film with a thickness of about 50nm. A sol PbTiO3 thin film was deposited on a Pt/TiO2/SiO2/Si substrate by a spin coating process. To form a noncrystallized PbTiO3 thin film, the sol PbTiO3 thin film was annealed at 450 degrees C for 1h. Locally crystallized nanodots were formed by the local crystallization process using an atomic force microscopy tip heated to 700 degrees C. We adjusted the diverse diameters of locally crystallized PbTiO3 nanodots in the range from 200 to 400nm by controlling the local heating times.