PURPOSE: To enable improvement of sensitivity by betterment of the S/N, by intecting amount of electron beams absorbed in a pattern of non-dielectric material.

CONSTITUTION: On a mask-holder 5 holding a mask 1, a connecter 4 contacting electrically with an alignment mark 3 and by utilizing a scribe line, etc. between each chip of light-exposure pattern 2 on the mask, electric contact with the connecter 4 is realezed by transmission with the mark 3 and elongation of lead pattern to the neighborhood of the mask. On each of the connecter 4, a detecting resistance 8 is connected between ground terminals and when scanning electron beams 6 from an electron gun scaned over the mark 3, an electric current by the electron beams absorbed by the mark 3 flows from the connecter 4 through the resistance sown to the ground terminal and by this absorbing current, a position of the mark 3 is identified by detection of a voltage value generated in the resistance 8. By this arrangement, high-sensitivity detection becomes available by a good S/N.