1. An observation method using an electron beam, comprising: a step of mounting a specimen on a specimen stage; an enlarged image acquiring step of irradiating a predetermined area in said specimen with an electron beam while scanning the electron beam, and acquiring an enlarged image of a specimen internal structure in said predetermined area in said specimen by using the electron beam passed through said specimen; a diffraction image acquiring step of irradiating a specific portion included in said predetermined area in said specimen with said electron beam and acquiring a diffraction image including information of a crystal structure in the specimen in said specific portion in said specimen, formed by the electron beam diffracted in said specimen; a crystal structure information extracting step of extracting information of said crystal structure in said specimen from said diffracted image acquired in said diffraction image acquiring step; and a display step of displaying the information of said crystal structure in said specimen extracted in said crystal structure information extracting step so as to be superimposed on said enlarged image acquired in said enlarged image acquiring step.