a photomultiplier for converting an incident weak light into multiplied electrons to thereby output an electrical signal corresponding to the intensity of the incidence light . the photomultiplier comprises a photocathode for emitting primary electrons ; plural dynodes for emitting secondary electrons in response to incident of the primary electrons and multiplying first secondary electrons passing between the dynodes ; and shield means for preventing second secondary electrons emitted from a first dynode of the dynodes toward the photocathode from returning to the dynodes , thereby to reduce the generation of a residual pulse currents caused by the second secondary electrons and to accurately detect a main pulse current caused by the first secondary electrons .