A convergent charged particle beam apparatus includes an electron beam system
which
emits a converged electron beam, a vacuum chamber which is connected to the electron
beam system, and a stage which mounts a specimen and moves at least in one direction
inside of the vacuum chamber. An electron beam image observation unit observes
an electron beam image of a surface of the specimen. A height detector optically
detects a height of the specimen mounted on the stage by illuminating the surface
of said specimen with light and by detecting reflected light of the illumination
reflected from the surface of the specimen, and a controller controls a focus position
of the electron beam in accordance with an output from the height detector while
the stage is moving at least in one direction.
