PURPOSE: To efficiency emit electrons from dynodes in the inward side to dynodes in the outward side by providing projected electrodes for the dynodes in the inward side of a photo-electron multiplier in such a way as to prevent the electrodes from being affected by potential in the one step ahead stage.

CONSTITUTION: A grid 2 and a photo-electric surface 3 are provided for the light introducing side of a tube body 1 in a photo-electron multiplier, No.2, 4, 6, and 8 inside dynodes 5, 7, 9 and 11 roughly in a linear line form are interposed within the tube body 1, and No.1, 3, 5, 7 and 9 outside dynodes 4, 6, 8, 10 and 12 in a recessed surface form are arranged around said inside dynodes in such a way that a circle line is described so that an anode 13 is located at the focal point of No.9 dynode 12. In addition, a projected electrode section 14 is provided at least for one dynode out of the inside dynodes 5 through 11. And it is so constituted that the projected electrode section 14 is located close to the dynode in the one step ahead stage in such a way as to be bent roughly normal to the secondary electron emitting surface sides of sections 5a, 7a,... affected by the dynodes in the one step ahead stage wherein the effective area for emitting secondary electrons from the inside dynodes is widened so as to let a multiplication be thereby improved.