To provide a method for manufacturing a diamond electron source which forms with a sufficient controllability a spherical surface of a desirable top end shape for generating a large current/high focused electron beam and provide a diamond electron source.

The method for manufacturing a diamond electron source which includes a top end portion as a diamond electron discharging point includes a process A in which a top end shape of the sharp top portion is rectified to a spherical surface by using a focused ion beam processing unit and a process B in which a process-damaged layer formed by the process A is removed by an acid solution. After the process A and the process B in the method for manufacturing the diamond electron source, the top end becomes a spherical surface of the diamond surface and as a result becomes an optimal diamond electron source for generating a large current/high focused electron beam and surpasses a conventional electron source in electron source performance such as an angle current density and luminance or the like.