A multi-biprism electron interferometer is configured so as to arrange a plurality of biprisms in an imaging optical system of a specimen. An upper electron biprism is arranged upstream of the specimen in the traveling direction of the electron beam, and an image of the electron biprism is formed on the specimen (object plane) using an imaging action of a pre-field of the objective lens. A double-biprism interference optical system is constructed of a lower electron biprism disposed downstream of the objective lens up to the first image plane of the specimen.