Photon stimulated desorption from aluminum surfaces was studied by irradiating an aluminum chamber in the 1.3 GeV electron storage ring at the Synchrotron Radiation Research Center. Experiments on aluminum samples were also performed in an experimental station. The behavior of water vapor, the main concern in this work, was quite different from that of the other gases. A time delay between the peak of the H2O signal and the starting time of irradiation was observed. Effects due to different conditions such as beam current, pumping speed, and beam dose of the storage ring were investigated.