An electron microscope stage mechanism capable of performing high-accuracy positioning while limiting vibration and drift. An ultrasonic motor is used in a stage drive mechanism, and a fixing mechanism capable of increasing stop stiffness is combined integrally with the motor. That is, a structure in which a piezoelectric actuator of the fixing mechanism is mounted in a pre-load mechanism together with the ultrasonic motor is used. When the stage is fixed by the fixing mechanism after acceleration, deceleration and positioning of the stage performed by the drive mechanism, the piezoelectric actuators positioned on opposite sides of the stage are extended to press the stage.