The effect of injected charges on fluorescence of organic thin films consisting of the donor molecule tetra(N,N-diphenyl-4-aminopheny-1)ethylene (TTPAE) was investigated. Fluorescence was efficiently quenched by charge injection. By comparison of fluorescence measurements and current measurements, it was found that hole injection had essential role in fluorescence quenching and electron injection did not. Coulomb interaction between photoexcited molecules and injected carriers was found to cause fluorescence quenching.