An apparatus according to the present invention for irradiating a specimen with charged particle beams comprises a single charged particle generating source (1) from which the charged particle beams formed of electrons and negative ions, respectively, can be simultaneously derived; a specimen holder (2) on which the specimen (11) is placed; and charged particle irradiation means which is interposed between the charged particle generating source and the specimen holder in order to focus the charged particle beams and to irradiate the surface of the specimen with the focused beams, and which includes at least one magnetic lens (M 1 M 2 ) and at least one electrostatic lens (E,, E 2 ) that are individually disposed.