A scanning electron microscope in which the secondary electrons generated from a specimen are efficiently caught by a secondary electron detector by correcting and controlling the trajectory of the secondary electrons is disclosed. A first auxiliary electrode impressed with a negative potential of several to several tens of volts is arranged in the vicinity of a radiation hole of the primary electron beam under an objective lens, and a second auxiliary electrode impressed with a positive voltage is arranged on the side of the first auxiliary electrode nearer to the secondary electron detector thereby to correct and control the trajectory of the secondary electrons. Further, a third auxiliary electrode for assisting in catching the secondary electrons generated from the specimen is arranged on the front surface of the secondary electron detector.