A specimen preparation device prepares a cross section of a specimen by applying an ion beam, the specimen preparation device including: an ion beam generator that generates the ion beam; a specimen holder that holds the specimen; a shield plate that shields part of the specimen from the ion beam; and a tilted plate that is placed to intersect a path of the ion beam on a downstream side of the specimen, and has an incidence surface that is tilted relative to a direction in which the ion beam is incident.