The development of a liquid-xenon photon detector is in progress for an experiment searching for μ +→e +γ at Paul Scherrer Institut (PSI). The detector utilizes liquid xenon as a scintillation material. The scintillation light is observed by photomultiplier tubes (PMTs) immersed in a liquid. An energy resolution of 0.76% is reasonably expected for 52.8 MeVγ rays from results obtained with a first prototype, where the active volume of 2.3 l is viewed by 32 PMTs. Another prototype has been constructed with an active volume of 80 l and 228 PMTs. The performance of the detector will be tested using laser-induced compton backscattered γ rays up to 40 MeV .