The reliable beamline structure for synchrotron radiation lithography has been investigated using the Photon Factory storage ring (2.5 GeV). The recently built beamline aims at attaining system reliability and safety. This beamline, one of three branch lines split from a basic beamline, is a 10−7Pa ultrahigh‐vacuum system with an oscillating mirror. In addition to a 40 ms fast closing valve (FCV) and an acoustic delay line (ADL), installed in the basic beamline, a<15 ms FCV and 40 ms ADL were set up to protect the storage ring from accidental breakdown. The FCV and ADL were placed far upstream of the oscillating mirror, to cope with accidental gas leakage caused by the oscillating mechanism. A vacuum breakdown test demonstrated that the FCV and ADL are greatly effective in vacuum protection. In order to protect operators from x‐ray exposure, two auxiliary shutters made of tantalum were placed upstream of the oscillating mirror. The oscillating mirror, driven through bellows by a combination of a direct current servomotor and a cam mechanism, enabled a highly reliable oscillation. A double‐structured bellows was adopted to provide against gas leakage. In addition, a silicon carbide plane mirror (40×17×4 cm) was employed because of its high‐heat‐resistance capability.