Example embodiments are directed to a scanning electron microscope. The scanning electron microscope includes an electron gun to configured irradiate an electron beam on a sample, and a disc of a transparent material and including a through-hole through which the electron beam passes. The disc includes a scintillator layer formed at a surface thereof so as to generate photons based on the secondary electrons received from the sample. A reflecting layer is formed at an inner peripheral surface of the through-hole so as to reflect the photons, thereby preventing leakage of the photons via the through-hole.