Nanocomposite films of poly(ethylene terephthalate)(PET) and nano titania(TiO2) were prepared by melt compounding with a twin-screw extruder followed by hot pressing for the purpose of investigating antibacterial activity. FE-SEM, EDS and XRD measurements confirmed that nano TiO2 was successfully dispersed at the level of individual particles in the PET matrix. Silver was introduced through photocatalytic reduction by nano TiO2 under UV (254 nm) irradiation to the nanocomposite films after being immersed in aqueous solution AgNO3 (100 ppm Ag ion). Even at 1 wt% of TiO2 content, the nanocomposite with silver photodeposition exhibited strong antimicrobial activity against Klebsiella pneumoniae and Staphylococcus aureus in measurement by shaking flask method.