To obtain a SEM capable of both providing high resolution at low acceleration voltage and allowing high-speed elemental distribution measurement, a SE electron source including Zr\u2014O as a diffusion source is shaped so that the radius r of curvature of the tip is more than 0. A Ni film is formed on the SnO2 film by an electroless plating method. The clamping member in the stowed position may serve as the handle by which a user grasps and operates the shaft. The client private key is securely provided to the client VM, which retains it only non-persistently. The system responds to an amount of force caused by an impact and disperses the force accordingly at a controlled rate. According to the invention, the calculated change in filling level is determined from a measured change in temperature of the liquid.