The c-axis oriented and epitaxial PbTiO3 thin films have been prepared by rf-magnetron sputtering for the high sensitive pyroelectric infrared sensor. It was found that pyroelectric currents were detected on these films even without poling treatment. The polarity of the currents were the same in all specimens. One of these films had εr of 110 and y of 2.5×10-8 C/cm2·K. Temperature dependence of εr of the film with and without substrate were measured. Whereas the film with substrate had the broad peak of εr at 550°C, the film without substrate showed the sharp and large peak of εr at about 600°C. A substrate free thin film infrared sensor was fabricated. The vlotage responsivity and relative detectivity are 1300 V/W and 2.5×108 cm√Hz/W with bandwidth of 1 Hz at chopping freqency of 10 Hz, respectively.