A sliced specimen preparing apparatus prepares a sliced specimen by slicing a surface of a specimen block in which a specimen is embedded in an embedding-substance. The apparatus includes: a cutter configured to slice the surface of the specimen block; a surface exposure determination unit configured to determine whether or not the area of a specimen portion on the surface of the specimen block is sufficient for the preparation of the sliced specimen; and a specimen block transporting unit configured to transport the specimen block between the surface exposure determination unit and the cutter. The surface exposure determination unit includes a humidifying unit configured to humidify the surface of the specimen block; an irradiating unit configured to irradiate the surface of the specimen block with light; an imaging unit configured to receive reflected light from the humidified surface of the specimen block which is irradiated from the irradiating unit to acquire image data; an image data processing unit configured to discriminate the specimen portion on the surface of the specimen block from the embedding-substance portion based on the image data acquired by the imaging unit; and a controller configured to control the imaging unit, the irradiating unit, and the image data processing unit, and to determine whether or not the area of the specimen portion on the surface of the specimen block, the specimen portion being acquired by the image data processing unit, is sufficient for the preparation of the sliced specimen.