PURPOSE: To reduce the delay of a deflection response to a deflection signal by providing a cylinder the surface of which facing to the electron beam pass is knurled in the deflecting coil.

CONSTITUTION: A cylinder 11 comprising conductive material the axis of which is the electron beam pass is provided between an electron beam generating chamber 1 and sample chamber 4, and the inside is maintained vacuum. Knurls, recesses, or waves are provided on the surface of the cylinder 11 facing to the electron beam pass through which surface the magnetic field from an electromagnetic deflecting coil 6 permeates. The eddy current is greatly reduced by providing knurls to lengthen the flowing pass of the eddy current to increase the resistance, and thus the magnetic field formed by the eddy current is minimized and the delay of a deflection response to a deflection signal is greatly reduced.