A sample preparation method is provided where chipping of and damage to a film at an observed location does not occur when cutting with a machining blade is carried out in advance in order to prepare a sample for use with a transmission electronic microscope. The surroundings of an observed location are grooved using a focussed ion beam prior to performing cutting with a machining blade so that the observed location can be isolated from the film composing the sample in a floating island shape. A thin-film for embedding may then be deposited with respect to the grooving, using a focussed ion beam. If necessary, a protective film can also be prepared at the surface of the observed location using a focussed ion beam.