The present invention relates to a photomultiplier having a structure for performing a high gain and achieving a higher productivity in a state keeping or improving an excellent high-speed response. In the photomultiplier, an electron-multiplying unit, placed in a sealed container, has a structure that enables an integrated assembly of a focusing electrode, an accelerating electrode, a dynode unit, and an anode. Specifically, by providing a structure for fixing directly the focusing electrode and accelerating electrode at a part of a pair of insulating support members for grasping directly the dynode unit and so on, together with the dynode unit and anode, each of the focusing electrode and accelerating electrode is aligned by using the pair of insulating support members as a reference. As a result, on assembly of the electron-multiplying unit, alignment work with high precision between the members, specific fixing members and fixing jigs becomes unnecessary, which enables to improve drastically the productivity of the electron-multiplying unit placed in the sealed container.