Effect of silver nanoparticle (AgNP) on the generation of singlet oxygen (1O2*) using a rose bengal (RB) as a photosensitizer for photodynamic therapy (PDT) were examined by measuring the phosphorescence spectra of 1O2* from RB-AgNP composite film and RB film on glass plates in CCl4. 1O2* was successfully detected by direct observation of the characteristic 1O2* phosphorescence around 1275 nm in two films. The excitation spectra of 1O2* in two films were in agreement with the absorption spectrum of RB in RB film or in acetone solution. The results indicates that the generation of 1O2* is ascribed by the PDT type Ⅱ reaction. The phosphorescence intensity of 1O2* in RB-AgNP composite film was larger than that in RB film. The enhancement of the phosphorescence intensity of 1O2* is most likely attributable to large electric fields due to localized surface plasmon resonance of AgNP aggregates.