PURPOSE: To provide a secondary electron detector which can selectively detect a specific energy secondary electron.

CONSTITUTION: Of a secondary electron(e), a relatively high energy electron e2, passing through the third electrode 7 of mesh shape applied with -200V voltage, is absorbed by being made incident to the forth electrode 11 applied with positive high voltage. On the other hand, a relatively low energy electron e1 is reflected by a negative electric field of the third electrode 7 of mesh shape, to pass through the second electrode 5 applied with +100V voltage, to be made incident to a scintillator 13. The scintillator 13 emits light in accordance with a quantity of the incident secondary electron e1. Emitting light in this scintillator 13 is advanced into a photoelectric transfer surface 16 of a photomultiplier tube 15 through a glass member 12 and an optical fiber 14 and converted into an electric signal.