The present invention provides a method and apparatus for correcting an aberration in a charged-particle-beam device. The apparatus includes a charged-particle-beam source, a charged-particle optical system that irradiates a specimen with charged particles emitted from the charged-particle-beam source, an aberration corrector that corrects an aberration of the charged-particle optical system, a control unit that controls the charged-particle optical system and the aberration corrector, a through-focus imaging unit that obtains plural Ronchigrams in which a focal position of the charged-particle optical system is changed, and an aberration calculation unit that divides the obtained Ronchigram into plural local areas, and calculates the amount of the aberration based on line focuses detected in the local areas.