A scanning electron microscope having a charged particle device that processes a specimen using a charged particle beam, the scanning electron microscope includes: an electron source; a secondary-electron detector that detects secondary electrons generated from the specimen; a backscattered-electron detector that is disposed closer to the electron source than a detection surface of the secondary-electron detector to detect backscattered electrons generated from the specimen; a shielding plate for shielding a detection surface of the backscattered-electron detector; and a moving mechanism that moves the shielding plate. In a state where the shielding plate is moved by the moving mechanism so as to shield the detection surface of the backscattered-electron detector, the shielding plate is located between the detection surface of the backscattered-electron detector and the detection surface of the secondary-electron detector.