To provide a semiconductor electron beam detector having sufficient detection sensitivity even at an acceleration voltage of about 100 kV, which can be easily loaded onto a package.

For this semiconductor electron beam detector, an electron beam detection part formed of a P-type diffusion region is arranged on the surface of an N-type first semiconductor substrate, and a second semiconductor substrate is arranged at least on the electron beam detection part. By the second semiconductor substrate, a distance for which an electron beam advances to the first semiconductor substrate is limited. Thus, the number of electrons to be detected is increased, and sensitivity is improved. Also, an electrode can be arranged only on the incident plane of the electron beam. Thus, mounting to the package is facilitated, and a manufacturing cost is reduced.