A method of manufacturing an electron multiplier body, the method includes a step of preparing a first plate-like member having a surface and a back surface and a pair of second plate-like members, a step of forming, in the first plate-like member, a hole portion reaching from the front surface to the back surface, a step of constituting a laminated body by laminating the first and second plate-like members on each other so that the first plate-like member is interposed between the pair of second plate-like members to form a channel defined by the hole portion in the laminated body, a step of integrating the laminated body, a step of constituting a main body portion by cutting the integrated laminated body so that the channel is open, and a step of forming a resistive layer and a secondary electron multiplication layer on an inner surface of the channel.