A charged beam exposing method comprises a step of applying a voltage to a sample to thereby form an acceleration electric field on the sample, a step of accelerating an electron beam emitted from an electron gun and scanning an alignment mark formed on the sample with the electron beam, a step of detecting back-scattered electrons and secondary electrons, generated from the alignment mark, by means of a detector, a step of acquiring the position of the alignment mark based on a signal waveform detected, a step of eliminating or reducing the acceleration electric field by changing the applied voltage to the sample, and a step of exposing a pattern with the electron beam emitted from the electron gun based on information of the position of the alignment mark.